How to change the name of external inputs/outputs in generated code?

Hello all, I am using embedded coder and I cannot figure out how to change a default on the generated code. Every time my code generates I get something like this:

typedef struct {
real32_T In1;              /* '<Root>/In1' */
real32_T In2;              /* '<Root>/In2' */
real32_T In3;              /* '<Root>/In3' */
} ExtU;

Invalid use of operator.

Error in connector.internal.fevalMatlab

Error in connector.internal.fevalJSON

Now majority of this is just fine, but I want the ExtU to be auto generated with ExtU_FileName. I cannot find a setting to modify that. Same goes for the output struct. I want it to be ExtY_FileName

/* External outputs (root outports fed by signals with default storage) */
typedef struct {
  real32_T out1;    /* '<Root>/out1' */
  real32_T out2;    /* '<Root>/out2' */
} ExtY;

The reason I need this is I am using quite a few generated code files and for clarity I want the structures to be associated with the file names. How can I go about doing this without modifying the code by hand?