How can I make the display text in a combo box invisible?

I use Access 2010.
I have a combo box in a form. I use the combo box to find and display a specific record.
When I click on the arrow of the combo box, I want to see the list in black text as by default.
After selecting I want the combo box text to be invisible. (Equal to the background color.)
The reason is that after selecting and while I navigate the form in other ways. I do not want to see the last selection that I made.