Haha, yes the declaration should be static void CALLBACK etc. well done ryan :)

The actual problem is that the compiler is expecting a void (_stdcall*) (arglist...)function and your function has somehow been defined as a mere void (arglist...) function hence the error. Since the CALLBACK statement defines the (_stdcall*) you should not be having this issue, unless the EXPORT statement is doing something dopy (so try removing it), or the TimerTakeSample referred to in the SetTimer function is being linked to a different function? try specifying COxygraphView::TimerTakeSample(blah...) in your SetTimer function to make sure your linkage is correct (can't tell from your example where the SetTimer is being called from). I'm sure the answer will reveal itself :)

The problem is with the declaration of your TimerTakeSample function. I think its probably got something to do with that EXPORT (try removing it?) because the CALLBACK simply defines the function type as an _stdcall* and so that should compile.