how to disable changing workdate - Nav 3.01

I have a idea, that is, just some of end users are allowed to post from today to the last date of the month. The other users are allowed to post from the first date to the last date of the month. The below is my solution: In user setup, set posting allow-from/to date. Perhaps I can write some code to update the date field every date in user setup table according to the permssion setup. But there is still a confusion. If the user change the work date, it seems that he still can post. Any ideas? or other good solution.

Actually, what is being checked during posting is the posting date, not the actual date or the work date. The meaning of the allowed posting period in user setup is not to set a date range during which the user is allowed to actually perform the posting operation, but to set the date range into which the to-be-posted entries are allowed to be posted into (does this make sense? [;)]). If you want to restrict the actual posting operation, you will have to modify the checking routines. In our 2.60, this is CU 11 for the G/L posting routines, which, by the way, will not require a solution developer license.