Cycle through combo box with keyboard

I have a datagrid that has a combo box column. Within that column I have about 30 items.  Now when I select the combo box and press a letter on the keyboard it shows me the first item in my combo  that starts with that letter.  The problem is that it pauses for a few seconds before I can press the letter again to get the next value.  Is there a way to speed this up so I can press a letter multiple times quickly to get to the 5 item that starts with that letter?

Thank You