>Can C functions be used issuing DECLARE in MSVCRT.DLL VFP as API ones are used?
Sure you can, just as you listed above, and just like you would call a Win32 API function. There's plenty of fun stuff in the C runtime that you may not find anywhere else. For instance, there's _fpreset(), which is used to fix a bug in many printer drivers. I used that function in the article because, hey, guess what, there's no other way to reset the FPU (at least none that I found).