I did some toying around before posting. I found that a dialog can use $iif to select between different values, and that you can use %global_variables to provide user-created data, but using a regular "if () {}" statement caused the dialog to stop working.

Are there workarounds to this? I've been wanting to work with this stuff for a while, but I just haven't gotten around to it until now, and I think it'd be rather useful.