passing extra parameters in optimization

If my objective run simple operation and also call other sub-functions and each sub-function has own parameters and may be they can share some parameters the following example is a view to how look like my objective function :

    function y = MyObjFun(.)

    some simple operation that need variables that do not change during the optimization.

    a = x1+x2;   

    y1 = sub-function1(a,b,c);
    y2 = sub-function2(b,d,e) 
    .
    .
    .
    ym = sub-functionm(m,n)

    y = y1+y2+y3ym;

what is the best way to write my objective function and passe these parameters?