Scenario: Sharepoint form created in infopath with multiple views. One multiple choice lookup column needs to be "Cannot be blank" for only one of the views. I have removed the ribbon save button and added my own, and put some rules on it to disable it if values are not entered correctly. This works for all validation conditions except for this multiple choice lookup field, were the field is always calculated as having a value = not blank, so the save button is never disabled.
So how do I set up conditional validation on a multiple choice lookup field?