[Zope] Trying to get Form/Checkbox value into Python Script

I've found the problem with getting data into a python script. It is with the checkboxes. If the checkbox is checked, the parameter is passed and the boolean property is set properly. However, if the checkbox is unchecked, I get a Zope error indicating that the parameter was NOT passed. Same form, same everything except in the test second test case the checkbox was unchecked. In essense, it only passes the checkbox value when the checkbox is checked. Does anyone know what I'm doing wrong? How do you pass boolean values (i.e., from checkboxes) to a python script when the box is unchecked? Thanks, Ron