I have tried the following:-
LIBRARY: vfxsupp64.dll
EXTERN: int "C" VXFSuppFindConstant(*);
but when I try to use VFXSuppFindConstant I get ERR: undefined word
Look in the file Kernel\x64Win\VfxSupp64.fth and use the word
`: isWinInteger? \ caddr len -- d|n|X 2|1|0`
Note that this word is in the SYSTEM vocabulary.