using maskedit control to allow entry and then scrolling a dblookupcombobox to closest match

For simply nefarious reasons, I want to have two MaskEdit controls on a lookup form. The first lookup box is to allow finding a patient by patient number. As you type in the patient number, a dblookupcombo box at the bottom of the screen opens and the matching name and patient number is shown.

The second maskedit control allows the user to search by name. Again, as you type in the name, the dblookupcombo box opens and scrolls to the nearest match.

My problem is that I cannot determine what to do to cause the dblookupcombo box to show the current record as selected. The record always appears in the middle of the scroll box, but is not highlighted. Is there any way to force the record to be selected. I have tried setting the KeyValue to the current patient number, but still no highlight.

Any light on the subject would be appreciated.

Thanks in advance,
Barry