Say the button is [cmdDesign] and the login group is [UserGroup].
On the Current event of the form, place this one-liner:
In case you haven't played with events before, set it up like this:
In the Form properties, pick the Events tab.
Double-click the blank line next to Current. You'll see Event Procedure.
Click the Builder (...) button at the right of the line, and you'll see the code module.
In the blank line in the routine, paste the code above. You will need to change control and field names to suit.