Using PWork Vector in .tlc file in MATLAB

Question

I am trying to use PWork vectors in a custom S-Function. I am hoping to use them to store a pointer to a DLL that I need to use.

In my mdlInitializeSizes I have:

ssSetNumPWOrk(S,1);

In mdlRTW I have:

static void mdlRTW(SimStruct *S)
{
    if(!ssWrteRTWWorkVect(S, "PWork",1,"PworkDLL",1)) {
        return; /*An error will be reported by SL*/
    }
}

In mdlStart:

#define MDL_START
    void mdlStart(SimStruct *S){
    real_T *xD = ssGetDiscStates(S);
    HINSTANCE dllptr = LoadLibrary("TactorInterface.dll");
    void **Pwork = ssGetPWork(S);
    Pwork[0] = dllptr;
    //ssSetPWorkValue(S,0,dllptr);
    WritetoVibrotactor_Start_wrapper(xD,Pwork);
}

I need to also implement this PWork in the .tlc file but I have no idea how to do this correctly. There doesn't seem to be much documentation or examples for how to do this correctly. I do have this so far in the .tlc file:

%%Function: Start ========================================================
%function Start(block, system) Output
/* S-Function "WritetoVibrotactor_wrapper" Block: %<Name> */

%assign pxd = LibBlockDWorkAddr(DSTATE, "", "", 0)
%assign pwd = LibBlockPWork(PworkDLL, "", "", 0)
WritetoVibrotactor_Start_wrapper(%<pxd>,%<pwd>);
%%
%endfunction

In my wrapper function:

void WritetoVibrotactor_Start_wrapper(real_T *xD, void *Pwork)
{
 HINSTANCE hGetProcIDDLL;
 hGetProcIDDLL = (HINSTANCE)Pwork[0];
 // void * hGetProcIDDLL = LoadLibrary("TactorInterface.dll");
 InitializeFn _InitializeTI = 
(InitializeFn)GetProcAddress(hGetProcIDDLL,"InitializeTI");
 //other stuff...
}

If I try to build the model I get an undefined identifier PworkDLL in the .tlc file.