Find a function in the function list
[C++]
CXllFn* FindFn(
   LPCSTR pszFnName
);
Pointer to a null-terminated string containing the exported name of the function (i.e. the name visible in Excel).
Returns a pointer to the function if found, and NULL if it cannot be found.
Header: xllplus.h
CXllApp Class 
					  | CXllApp Methods			 
					  | CXllApp::AddFn()			 
					  | CXllApp::RemoveFn()