We have a form displaying our Opportunity Pipeline.  One few the Fields is Projected Close/Award Date, PoP Start, and PoP End.  We've been manually pushing the PoP Start, and PoP End Date to the right as the Projected Close Date expires.  We have the ability to convert a opportunity to an Active Program or mark it as lost once we've been awarded the contract or have lost it.  I'd like to automatically update the PoP Start and PoP End date based on the Projected Close Date in comparison to Date().  I added an unbound field with the expression:

=IIf([Projected Close/Award]>(Date()+30),[PoP Start],DateSerial(Year(Date()+30),Month(Date()+30)+1,1))

The problem with this is I would have to expose both PoP Start, PoP End, and the unbound calculated fields so whoever is entering/updating the opportunities.  I'd like to only have one field and have the logic behind that field to display the entered pop date unless certain criteria is matched.  I'm assuming I'll need to use DLookUp, a separate form for with the PoP Start date and then the critera.  Am I heading in the right direction?