isn't your idea for printing purpose ?
So it seems... I do not see other realistic purposes.( If a field is empty, why cover it with white "n" chars ? )
"My problem is that I can use the wingding font in a text box, but I cannot get it to work in a calculation field."
Any calculation ( result text ) field can handle wingding font, even with font locking active: hold down Ctrl + Alt while chosing the font.
I have text screens and pictures used as buttons on a menu screen that need to be hidden until the user goes to preferences and types text into a Main Menu item field which will then show the text and the button for the user to use on the Main Menu.