Well, CSupParseFunctionParams() is a helper function which wasn’t intended to be ‘exported’. It is because it expects specific input which isn’t normaly available. It expects function declaration but can handle a call as well.
Anyway, your macro uses it creative way and it should work with no problem if you’re able to capture whole parameter list. There can be a problem: your search expression probably won’t work if GetMatchGroup() call is written on multiple lines or if one of parameters is another macro call (nested parentheses).
BTW, it shouldn’t be necessary to call CSupInit() as it is called from TipWin initialization which should be already called when MEW is started.