1) Main_image_id with variables      

            a) Main_id

            b) Main_complete (numeric variable currently all set to 0) <-- I want this value to be turned to a 1 on submit from form 2 (Images)

      2) Images

            a) Main_id <--from lookup dropdown referencing Main_id in form Main_image_id

            b) bunch of other fields.

What I want to do is when the submit button is selected I want to change Main_complete = 1. Then I want to filter the lookup dropdown list to only show the Main_id where Main_complete=0.

Currently I have set the filter to Main_Completed==0 which shows all the Main_id's but how do I change the value to 1 after they submit the record?