Populate text boxes from selection in 2nd Dropdownlist filled based on selection in 1st Dropdown list

I have a webform containing two dropdownlists and four text boxes.  The first dropdownlist populates on pageload with customer names and datavalue of customer ID.  Based on the selection in that dropdownlist two text boxes are filled from SQL Db.  Those are account manager and customer contact.  Along with those text boxes populating, I also have a 2nd dropdownlist filling with based on the customer id that pulls all parts specific to that customer.  In order to properly fill that second dropdownlist I had to remove the datasource and generate it in the code behind fired from a ddlCustomer_selectedIndexChanged event.  All of this is working perfectly.
The problem I'm having is that based on the selection of the 2nd dropdownlist I need to populate two additional textboxes, part description and customer part number.  Here in lies the problem.  I've called the fill of these two later textboxes with essentially the same code as the ...