Wow, you can always tell the Excel users that think Access is "advanced Excel".
A Pivotchart? Really? What is it you're trying to do in English terms, not Excel terms? You're getting the ID numbers associated with the employee names. Did you import the names from Excel and then have Access auto-assign a primary key? (That's my guess here.)
I seriously have no idea how a pivotchart would be useful in a table/form of employees, and I can be wrong, but I think you're thinking Excel and getting seriously confused by Access. I understand that you're trying to get to a chart of training hours, but I think you've gone far down the wrong path and need to rethink what's actually happening here.
If your chart is working fine and your just getting the number for an employee instead of their name, then you just change the column width properties of the combobox. Leave the bound column to the employee number as that's the key, but give it a column width of 0 so that it doesn't appear.
If I'm way off base, then I'm sorry, but your question wasn't worded well and I was going by experience as to what was really going on. Please elaborate more.