My requirement is they can submit multiple report's name with email associate with the report, and they can either add or remove the report. My original design could cause some confusion because they might think first I select 'Add' then put 3 reports in MRVS, then later select 'Remove' with 2 other reports. The assignment group will interpret as Remove them all, so I think if the MRVS isn't empty then set the selection field to be Read Only omit them to change.

If this isn't achievable then I might addErrorMessage whenever they change the variable that states you can only do 1 action per request