Combo Box- typing filter

I have a read only combo box. Is there a way to let the users type a letter and the combo box automatically filter down to those values that begin with that letter while still being read only?
Thanks!

AS:

Do expect to pull values from a database?

I have a drop down list of values, and on Keypress of a letter I would like it to jump to that section of the drop down.

javascript.forum.17612.2/combobox-and-grid-combobox-autocomplete.html