If I type very quickly, then the list narrows to the correct item,

If I type too slow, then the list always goes to the item that starts with the letter I just typed.

i.e.  If we were to use state abbreviations as an example...

If I type M, then the combobox will select ME. (the first of the M's)  If I was wanting the abbreviation MD, and I then slowly type a 'D' after the 'M', then the combobox goes to DE, not MD as I would expect.  HOWEVER ! ! ! IF I TYPE MD REALLY QUICKLY, then it works. 

Is there some type of event handler that I need to code to change the behavior to what I would expect?

Thanks!

Doug