Using a Calculation field for a Portal

[Joseph31]

I have a very Simple Portal -- The Portal shows "Amount Due" & "Date Due"

I came up with a calc field on the page where the portal sits.. Very simple:

When "Date_Due" is < 30 days show a "1"...

Now this field is a calc field... so when I go to make a portal on another page that shows all of the "1" nothing happens...

How do I get a portal to index off of a calc field that cannot be indexed?

Recap:

All I want to do is to make a portal show all of the cases where due date is less than 30 days?

Help...

Joseph