page usage based on part of a string in data

We are using create resource to pull in tons of PDFs. The PDFs are all single page. They have the page number in the file name (xxxxx.p1.pdf, xxxxx.p2.pdf

We want to change the page usage based on the part of the file name (.p1.pdf).

The rule would look something like this.

if data has ".p1.pdf" in the record then use page 1

else use page 2.

I understand how to use 'FusionPro.Composition.SetBodyPageUsage' but not the other part.

FPD 5.1

Mac 10.4.11

Thanks,

Ryan