>It may be the APPENDS that are causing the problem
>but how can I need to let users add records constantly
>so what can I do ?

In general you have to repeat the attempt.

From VFP Help for SET REPROCESS command:

"The first attempt to lock a record or file isn’t always successful. Frequently, a record or file is locked by another user on the network. SET REPROCESS determines whether Visual FoxPro makes additional attempts to lock the record or file when the initial attempt is unsuccessful. An ON ERROR routine affects how unsuccessful lock attempts are handled."

Check also help to SET MULTILOCKS command.