Hello,
just a guess (don't know if this is possible):
setting up a folder for which only one special user has the rights
then in your program impersonate to that user and access the folder ..
how to impersonate at runtime to another user is handled in one of Rick Strahl's whitepapers at
www.westwind.com (one dealing about ASP with FoxPro, don't know the exact name now ..)
another solution migth be using the WINAPI function "CreateFile" to open files/folders exclusivly
the drawback would be that you'd have to use also the other WINAPI file related functions such as ReadFile/WriteFile etc. to access the files for processing them
if you'd tell us why exactly you want to whole folder to be "reserverd" for your process maybe someone has another idea/concept to handle the "whole" situation
Regards
Christian