Oracle Forms

I need a way to mark an "X" instead of a "checkmark" within a form. I created a new data block text item (instead of an actual checkbox item) which, upon clicking, will toggle the value of the item between an "X" and an empty string, which works fine.

However, I need a way to disable the item so that the user cannot actually type a value into the item during runtime. If I disable the item or disallow Insert, then the clicked trigger will not fire.

Any suggestions?