See solution in other versions of Access:
Question: On an Access 2007 form, I've created a combo box whose values are populated by a query. I want to see the column headings so that I can differentiate between the various columns. How do I display the column headings in a combo box?
Answer: Even though you can only bind the combo box to one column, it is possible to display multiple columns when you click on a combo box. This is often useful when one field in a result set is not enough to differentiate between the different records. For example, you may have multiple suppliers called IBM, but each IBM supplier is uniquely identified by its address.
To display the column headings in a combo box, open your form in design view. Right-click on the combo box and select Properties from the popup menu.
On the combo box, there is a Property called "Column Heads". You will need to set this property to "Yes" on the combo box object.
You should now see the column headings (Company Name and Address) when selecting the combo box. See below: