more than one instances in S-function

Good morning! I have different problems with a S-function. First of all I have a cpp file, which is called dsp.ccp, and I have diferent S-function blocks calling to this file. If i want to save the values for each instance I have read that I have to use Work vectors (Is this correct?).

If this is correct I have another problem with this. The dsp.cpp file has functions that they are in other file, called acc.cpp. If I need to use the save values (different in each instance) in this file is the only possibility sending with the function call ( execute_acc(dwork) ), or can I create this work vectors variables inside of acc.cpp.

Sorry for my English, if there is any doubt ask please.

Thanks