I want to make a field lock so that even user Do Not use the system directly, some of the field are not allowed to edit or in my application, not allow user to edit that field!!

So, I use a Global Variable to control it and set the Update Validation on field in table definition to:
gAccessLevel > 500
Message for Invalid:
"Your Access Level is not enough to edit this field!"

But I wonder that even in browse window, if the gAccessLevel is not enough and I don't change the value of field, that invalid message still come out and nearly impossible to leave!

What are the better way to skip invalid message if low access user DO NOT edit that field but give an auto-reverse instead of system asked messagebox!?