having a graphic appear in field

[mozart11]

I want to create a field that is a checkbox that when I put an x into it, a graphic I have of a ? replace it. I assume the graphic has to be in a container, but I spent hours trying to make a calculation that if field mark is valid then container shows graphic. Haven't been able to figure it out.

Thanks. I hope this makes sense.

[dbruggmann]

- Create a global container field