InfoPath Dev

Scenario: 

1.  User puts in a start date, end date, and model#

2.  External Data Connection is queried for existing reservations (model, start date, end date display in a repeating table)

3.  Drop-Down Box displays all the ID's for the selected Model, not just the ID's available during that time.

Problem:  I want to reduce the drop-down box options to only show those without a schedule conflict. Please help convert my "Exclude" statements below to "include" statements InfoPath supports

1.  Exclude if desired Start date is in existing reservation range (after external start date and before external end date)

2.  Exclude if desired End date is in existing reservation range (after external start date and before external end date)

3.  Exclude if the desired reservation starts before & ends after existing reservation

**Update** 

I couldn't figure out how to reduce the drop-down box options as needed, but was able to apply rules to a button so that they can't proceed if they selected an invalid entry.