Opening Multiple Scenarios for Input and Running Business Rules

Hi,

Does anybody have a suggestion on how to make a business rule fix on different months depending on which scenario is used on a WebForm?  I am trying to make the business rule decipher what scenario is being used and then FIX on the months that are valid for that scenario?  I don't see a way to make a business rule perform an if statement to fix on the proper months for that scenario.

For example, If a user is inputting data on a form for SepFcst, then it should only run calculations for the months defined for that scenariom, which would be Sep - Dec.  If a different user is updating a Plan, then it should calculate Jan-Dec.