>>>Using FOPEN('some.exe',1) to check whether or not the exe is in use will give accurate results if the folder is readwrite. If fopen() succeeds, then the exe is not in use. If fopen() fails, then the exe is in use.
>>>
>>>However, if the folder is readonly fopen() will always fail, even if it is not in use.
>>>
>>>Is there another way (preferably an API) that can tell whether or not the exe is in use, no matter by whom or by what process?
>>
>>Enumerate the running processes instead
>>http://www.news2news.com/vfp/?function=-1&example=164
>
>Will this also work for an EXE that is on the network and used by others on the network?

You could run the code server-side.