How to make goal seek with 3 unknown varible that interconnected each other?

Hai, i want to search the output of Tb_of and Tb_hf in every iteration, but we just know both of the input value and the input value had a different enter region. to search that value in excel i have 3 stopping criteria, the first one is when absolute value of deltaTb_of is no more than 10^-5, second is when the value of Tb_hf iteration comes to more than input value of Tb_hf, and the third is when the last iteration value of Tb_hf more or less 10^-5 from Tb_hf input value or absolute deltaTB_hf is no more than 10^-5. as far as i wrote the code, i have some problem, the bigger problem is guessing value and iteration of Tb_hf never come to a convergence value so iteration for delta Tb_of and delta Tb_hf never reach the condition.

here is my calculation sheet in excel

and here is my iteration code now

while abs(deltaTb_hf)>=10^-5 %Stopping criterion of calculation

      Tb_of_0=Tin_of; %Declare initial bulk temperature of organic fluid is equal to inlet temperature of organic fluid
      DB(1,1)=L0;  %Record value of initial length
      DB(1,3)=Tb_of_0; %Record value of inlet temperature of organic refrigerant
      DB(1,7)=(refpropm('H','T',(Tin_of+273.15),'P',pressure.*1000,refrigerant))/1000; %Record value of initial enthalpy of organic fluid

      i=1;    %Iteration 0
      Tb_hf_0= Tb_hf_0+deltaTb_hf;   %Iteration for outlet bulk temperature of hot fluid
      DB(1,17)=Tb_hf_0;   %Record value of outlet temperature of hot fluid

      i=2;    %Re-declare calculation
      Tb_hf_i=Tb_hf_0+deltaTb_hf;  %Declare bulk temperature of hot fluid for start column iteration

      while Tb_hf_i<=Tin_hf %Column iteration

          Lnew=Lnew+Delta_L;     %Total Length
          deltaTb_of=1;   %Starting criteria to enter row iteration
          Tb_of_i=DB((i-1),3)+deltaTb_of; %Starting criteria to enter row iteration

          if i==2
              cp_hf_i=1.8363+(0.00392.*Tb_hf_i)-((1.5.*(10^-6)).*(Tb_hf_i^2)); %Starting heat capacity at constant pressure of hot fluid to enter row iteration
          end

          while absolute(deltaTb_of) >= 10^-5  %Row iteration

              Tb_of_i=Tb_of_i+(deltaTb_of/2);   %Correction for bulk temperature of organic fluid
              Tf_of_i=273.15+((DB((i-1),3)+Tb_of_i)/2); %Calculate film temperature of organic fluid in a segment in K

              h_of_i=(refpropm('H','T',(Tb_of_i+273.15),'P',pressure.*1000,refrigerant))/1000;    %Enthalpy of organic fluid in a segment
              Qdot_i=mdot_of.*(h_of_i-DB((i-1),7));  %Heat rate generate from organic fluid

              Tb_hf_i=Tb_hf_i+(Qdot_i/(cp_hf_i.*mdot_hf)); %Bulk temperature of hot fluid in a segment
              Tf_hf_i=(DB((i-1),17)+Tb_hf_i)/2;  %Calculate film temperature of hot fluid in a segment in oC

              %Physical properties of organic fluid from REFPROP
              rho_of_i=refpropm('D','T',Tf_of_i,'P',pressure.*1000,refrigerant);   %Density of organic fluid in a segment
              k_of_i=refpropm('L','T',Tf_of_i,'P',pressure.*1000,refrigerant).*1000;   %Thermal conductivity of organic fluid in a segment
              nu_of_i=refpropm('$','T',Tf_of_i,'P',pressure.*1000,refrigerant);   %Kinematic viscosity of organic fluid in a segment
              Pr_of_i=refpropm('^','T',Tf_of_i,'P',pressure.*1000,refrigerant);   %Prandtl number of organic fluid in a segment

              %Physiscal properties of hot fluid from formulae
              cp_hf_i=1.8363+(0.00392.*Tf_hf_i)-((1.5.*(10^-6)).*(Tf_hf_i^2)); %heat capacity at constant pressure of hot fluid in a segment
              rho_hf_i=870.297-(0.684497.*Tf_hf_i)+(5.18441*(10^-5).*(Tf_hf_i^2))-(1.0695.*(10^-6).*(Tf_hf_i^3)); %Density of hot fluid in a segment
              k_hf_i=0.1265-(0.000123.*Tf_hf_i)-(9.161.*(10^-8).*(Tf_hf_i^2));    %Thermal conductivity of hot fluid in a segment
              nu_hf_i=exp((645.13/(Tf_hf_i+117.8))-2.662);    %Kinematic viscosity of hot fluid in a segment

              %Calculation for organic fluid parameter
              vm_of_i=mdot_of/(rho_of_i.*A_ft);   %Mean velocity of organic fluid in a segment
              Re_of_i=(vm_of_i.*di.*10^4)/nu_of_i;   %Reynold number of organic fluid in a segment
              Nu_db_of_i=0.023.*(Re_of_i^0.8).*(Pr_of_i^0.4); %Nusselt number based on Dittus-Boelter of organic fluid in a segment
              hc_of_i=(Nu_db_of_i.*k_of_i.*(10^-3))/di;   %Heat transfer coefficient of convection of organic fluid in a segment

              %Calculation for hot fluid parameter
              vm_hf_i=mdot_hf/(A_an.*rho_hf_i);   %Mean velocity of hot fluid in a segment
              Re_hf_i=(vm_hf_i.*((Di+do)/2)/nu_hf_i).*(10^6);    %Reynold number of hot fluid in a segment
              alfa_hf_i=(k_hf_i/(rho_hf_i.*cp_hf_i.*(10^3))).*(10^6);   %Thermal diffusivity of hot fluid in a segment
              Pr_hf_i=nu_hf_i/alfa_hf_i;  %Prandtl number of hot fluid in a segment
              Nu_db_hf_i=0.023.*(Re_hf_i^0.8).*(Pr_hf_i^0.4); %Nusselt number based on Dittus-Boelter of hot fluid in a segment
              hc_hf_i=(Nu_db_hf_i.*k_hf_i)/((Di+do)/2);   %Heat transfer coefficient of convection of hot fluid in a segment

              %Calculation for heat transfer between both fluids
              Ln_T_i=log((DB((i-1),17)-DB((i-1),3))/(Tb_hf_i-Tb_of_i)); %Natural logarithmic bulk temperature in a segment
              UAs_i=1/((1/(hc_of_i.*A_si_i))+(1/(hc_hf_i.*A_so_i))+((log(do/di))/(2.*pi.*k.*Delta_L))); %Overall heat transfer coefficient in a cylinder

              %Check error
              Tb_of_pivot_i=DB((i-1),3)+(Tb_hf_i-DB((i-1),17))+(((10^3).*Qdot_i/UAs_i).*Ln_T_i); %The first guess bulk temeperature of organic fluid in a segment that synchronize with bulk temperature of hot fluid in a segment

              deltaTb_of=Tb_of_i-Tb_of_pivot_i;   %Convergence check for bulk temperature of organic fluid in a segment

              if abs(deltaTb_of) <= 10^-5

                  %Moving data
                  DB(i,1)=Lnew;   %Length to column 1

                  DB(i,3)=Tb_of_i;    %Bulk temperature of organic fluid to column 3
                  DB(i,4)=Tf_of_i;    %Film temperature of organic fluid to column 4
                  DB(i,5)=rho_of_i;   %Density of organic fluid to column 5
                  DB(i,6)=nu_of_i;    %Kinematic viscosity of organic fluid to column 6
                  DB(i,7)=h_of_i; %Enthalpy of organic fluid to column 7
                  DB(i,8)=k_of_i; %Thermal conductivity of organic fluid to column 8
                  DB(i,9)=Pr_of_i;    %Prandtl number of organic fluid to column 9
                  DB(i,10)=vm_of_i;   %Mean temperature of organic fluid to column 10
                  DB(i,11)=Re_of_i;   %Reynold number of organic fluid to column 11
                  DB(i,12)=Nu_db_of_i;    %Nusselt number of organic fluid to column 12
                  DB(i,13)=hc_of_i;   %Heat transfer coefficient of convection of organic fluid to column 13

                  DB(i,15)=Qdot_i;    %Heat rate generate from organic fluid to column 15

                  DB(i,17)=Tb_hf_i;    %Bulk temperature of hot fluid to column 17
                  DB(i,18)=Tf_hf_i;    %Film temperature of hot fluid to column 18
                  DB(i,19)=cp_hf_i;   %Heat capacity of hot fluid to column 19
                  DB(i,20)=rho_hf_i;   %Density of hot fluid to column 20
                  DB(i,21)=nu_hf_i;    %Kinematic viscosity of hot fluid to column 21
                  DB(i,22)=k_hf_i; %Thermal conductivity of hot fluid to column 22
                  DB(i,23)=alfa_hf_i;    %Thermal diffusivity of hot fluid to column 23
                  DB(i,24)=Pr_hf_i;   %Prandtl number of hot fluid to column 24
                  DB(i,25)=vm_hf_i;   %Mean temperature of hot fluid to column 25
                  DB(i,26)=Re_hf_i;   %Reynold number of hot fluid to column 26
                  DB(i,27)=Nu_db_hf_i;    %Nusselt number of hot fluid to column 27
                  DB(i,28)=hc_hf_i;   %Heat transfer coefficient of convection of hot fluid to column 28

                  DB(i,30)=UAs_i; %Overall heat transfer coefficient in a cylinder to column 30
                  DB(i,31)=Ln_T_i;    %Natural logarithmic bulk temperature to column 31

                  DB(i,33)=deltaTb_of;    %Error checking in row iteration to column 33

              end

          end

          i=i+1;  %New row iteration
          Tb_hf_i=DB((i-1),17);   %Stopping criteria for column iteration

      end

      deltaTb_hf=(Tin_hf-Tb_hf_i)/2;  %stopping criteria 

      if abs(deltaTb_hf)>=10^-5
          Lnew=0;
      end

end