Dashboard Tracker View Question

I have created a dashboard that will list all unconfirmed open purchase
orders. What I would like to do is add some search fields so the user
can filter out the results by one or all of three ways; date range,
purchaser name, and vendor name. I have the date range and purchaser
fields working as they should. The problem that I'm having is with the
vendor ID field. It is being added as a text box, and not a drop down
menu. I tried adding in an ultracombo for the vendor id, but when you
use it to filter by no results are returned. Anyone have any ideas on
howw I can accomplish this?