In layout mode, select the field and go to Field Control>setup.
On the left hand side tworad the top, you'll see a Display as option. Choose "Checkbox Set".
From your description, you would then want to "Display Values from" a custome value list of "Yes" and "No".
I'm not sure what you mean by "dummy variable"...but the context makes me think that I don't have to...
thanks for your response! I'm actually trying to NOT have it say yes/no next to it. but the program won't let me get away without having labels next to each box (so it looks like Yes<box> and No<box>). The dummy variable part is just that I want an indicator for something. So box is checked if certain requirements have been filled, and then when I write a script, I say "only perform script for records with a box checked".
I don't know if it works on later versions of FMP (I'm on 8 with dabblings in 9), but I used to simply decrease the field size so that only part of the checkbox set showed...i.e. the part I wanted to show.
In layout mode, select the checkbox field and drag/shrink it smaller and see if this approach still works. You'll end up with a "Yes & No" where only the "yes" part is visible on the layout.
Hmmm...I wonder if you made your value list simply "Yes" and left the "No" off of the value list if that would also do it...hmm
If you don't care what the value is and just want one check box, create a value list of one item only. That item could just be a single, invisible space character.
As Ninja said, you can resize the object to hide all but the check box. You could also change the text color to match the layout background.
All slightly different ways to get the same basic result.