Filter dropdown selection after record in the second table

So currently I’m trying to have Table A which has Users
I have Table B where I will record and assign a license for each user

I am using formula (Select(Users[Person ID],[Organization ID]=[_ThisRow].[Organization ID])
Where it filters the Users based on a ref by the Organization ID

When I save the record in Table B I need this to be filtered in the next time the user tries to add the same user again it doesn’t show in the dropdown again to avoid duplicates

You could try…
Select(Users[Person ID],[Organization ID]=[_ThisRow].[Organization ID])-TableB[Person ID]