Required funtion not processed

I'm new to VC, so this may be a silly question. I'm attempting to use BAPI_MaterialPhysInv_ChangeCount. When I attempt to commit the change, I'm receiving the error:

Required function MB_PHYSICAL_INVENTORY not processed

I should warn you that we're using the IS-CWM solution in the ERP environment and there are only about 4 of these implemented so far.

Any advise would be appreciated.