Flag out if a person has been nominated more than once

@bella28 ....I don't think it will be possible, but I can think of following 2 scenarios:

1. Scenario 1:
   • Create a view and show the Nominee count
   • Add a lookup control in your Nintex form and configure it to show the above created view and filter it by the Nominee value being pass in current form
   • Also put a label stating "Please do not submit form if Nominee count is 5 or more."
2. Scenario 2:
   • Let the users submit the form
   • Trigger the workflow and do query list and get the Nominee collection
   • Using collection operation get the collection count
   • If count is more than 5 then send notification to Created By person and then delete the item

You can use Scenario 2 with Scenario 1 too in case there is slightest possibility that users will disregard the message.