Comparing Date Fields to change the visibility of a subform

I have been trying to figure out how to compare date fields in LiveCycle Designer ES2.

I have two date fields: "First Draft Due" and "Final Due"

On exit from Final Due I want to automatically compare the fields. If they are less than 48 hours apart, I want to make the word "Rush" appear at the top of the form.

I have a hidden SubForm "RUSH" at the top of the form.

Any help would be greatly appreciated.

Thanks.