TComboBox problems

Hi,

    I have a TComboBox on my form and I add strings to it based on the
lastname that was entered (displays all firstnames associated with
lastname).  I can get this to work.  However, I am using the OnKeyUp
event for the edit box and for some unknown reason, if I match on a
lastname (the edit box), it enters in all firstnames for it, if I
press backspace or enter more characters, it displays the same names
randomly in the combobox for up to 4 characters more or less than the
lastname.  There should be nothing in there since there was no match,
and I have stepped through my code and it doesn't go into the loop
where I add them when there isn't a match (it's the only place where I
add them).  But it still adds them in and I don't know where they are
coming from.  Does anybody have any suggestions?  I tried using
OnKeyPress and got the same result more or less.

Thanks in advance
Ghost