Thank you both. Lynne, I tried using "post" first, but it didn't work, so I tried "show" after that (didn't work either). I'm not sure of the docs that help understand what to use where.
By "didn't work", I mean all evaluations of the field were 0, regardless of the set data.
So I'm wondering if I have any setup problems - is there something I need to make sure is done before this would work? Is there anything I can check?
I'm actually not interested in posting the field content, I just want to use it as a switch to do one of two different actions, that the user can select.
Thanks again.