How to block alt-Numberpad up/down keys generating altcode characters in a TEdit.

[MarkShark 27]

The situation:

I'm trying to emulate a combobox using a buttoned edit control and another parented control as the "box".  This works fairly well, but I want to handle the standard Windows combobox hotkeys for toggling the box visibility which are F4 (easy) and Alt-Up/Alt-Down (much less easy as it turns out since I almost always use the up down arrows on the numberpad.)

 

The problem:

Using Alt-Up and Alt-Down from the numberpad (as opposed to the up/down dedicated keys) generates alt code characters.  This happens even if the numlock is off (I was surprised by this.)

 

The only solution I've found:

I'm just filtering out the possible alt-code characters in OnKeyPress.  This isn't ideal as if you hold down Alt and just hit up or down like crazy you can generate a large number of different characters, and I'd like to filter them all or come up with a much better way than an overly large case statement.

 

Any thoughts or ideas?