Function to lock file
FLOCK([<workarea | alias>])
The FLOCK() function attempts to logically lock the currently selected table. If successful, it returns .T. and the table is locked. If the table is already locked by another user, it returns .F. If the optional <workarea | alias> name is specified the function will operate in the required location. The FLOCK() function does NOT change the open status of the table to 'exclusive'.
do while not flock() sleep 2 enddo