I'm creating a subscription center form where users can select checkboxes for types of communications they want/don't want to receive, which updates a "Preference" custom field. I wanted to build this so that if they uncheck all the boxes, they will update the preference field to a null value, which would in turn trigger a Smart Campaign that flags TRUE for the Unsubscribed Lead system smartlist, but not if there is a value in the field.
The problem is, the checkboxes work perfectly fine when 1 or more value is selected, but leaving all values empty will merely result in that field not being updated, rather than being updated with a null value. That makes sense and is certainly how I would expect it to work, but in this case it is not what I'm looking for. Does anyone have ideas on how a field could be updated with a null value when nothing is selected?