i am using auto increment to assign a number to a field automatically. However, every now and again, I need to change the number manually in the data. It's not allowing me to do so, says it's read only. I end up having to hit cancel and killing the application to get out of the routine.

More details;
I have consecutively numbered membership cards.
Each record has a unique card number assigned to it.
If I create a new record, then revert changes back, it increments the count ahead, even though a new record was not created.
So I have a useless membership card, unless I can go back and manually input the correct member number, that has already been passed.