Try the following API calls, may be it works that way you are looking for

* Locks a region in an open file.
* Locking a region prevents other processes from accessing the region.
DECLARE INTEGER LockFile IN kernel32;
	INTEGER hFile, INTEGER dwFileOffsetLow,;
	INTEGER dwFileOffsetHigh,;
	INTEGER nNumberOfBytesToLockLow,;
	INTEGER nNumberOfBytesToLockHigh

DECLARE INTEGER UnlockFile IN kernel32;
	INTEGER hFile, INTEGER dwFileOffsetLow,;
	INTEGER dwFileOffsetHigh,;
	INTEGER nNumberOfBytesToUnlockLow,;
	INTEGER nNumberOfBytesToUnlockHigh

FoxPro code sample
Locking FoxPro table
http://www.news2news.com/vfp/?example=154&function=230