Allow User To Update One Field Only

[Toby Young]

I currently have a table where User 1 can not update any
fields and User 2 has full permissions. This is set up
through the Access Security Wizard. I would like to make
it so that User 1 can update one field on a form and thus
the one field in the underlying table only, while User 2
still has full permissions.

I really just need a control button to be pressed by User
1 to update a field from "y" to "p" for that record only.

Any help/guidance on this matter would be greatly
appreciated.

Thanks for your help.