Hi Sharksfan! Sorry for the delay in responding.
If you want to filter what is returned from the server, you will have to use a Web Service. SharePoint provides a bunch of Web services, but I'm not sure if they allow filtering on a list. We do this a lot using our Database Accelerator. We filter the contents from SQL. In order to do the filtering there has to be some server-side code that takes a parameter and executes a filtered query based on it. You should read the SharePoint SDK and see if such a thing exists for SharePoint. My hunch is that it doesn't exist, so filtering the list of what is returned is not going to happen with SharePoint on the server, but I cannot give a definitive answer.
If you want to filter client side, you can do this in InfoPath. After you pull the items into a secondary data source, you can use a filter on top of that or write code. For best performance, you'll want to write a little code that copies the items you want into another secondary data source after query executes. Then, bind that field to the view. This will reduce the number of window handles created in the view. For large lists it can be a big issue. You can display count of items in list and use a conditional section to require users to type in a string and click a button to filter the list down before displaying. That wlil require some code. We'd be happy to help you write the code, but you'll need to send us your solution and buy a few hours of support credits.
Good luck!
Patrick Halstead / Microsoft InfoPath MVPQdabra® Software / Streamline data gathering to turn process into knowledge