Since you are using VS 2008, I would take a totally different approach than putting all that into the report's data source. Instead. use DataSet objects to create the final resultset and print from that.
It's perfectly fine to pass data from comboboxes to your report parameters, but you're creating a lot more work for yourself than necessary. If you wanted to do you, you can check out my CR Encyclopdia Book Vol. 2 for lots of VS.NET code samples. But going with the DataSet idea will save you a lot of headaches.
http://www.amazon.com/exec/obidos/ASIN/097495361X/bischofsystem-20