For another time, each character on your keyboard has a corresponding ascii number value of the key - i.e. in ascii, the letter A is equivalent to 65, B to 66 etc.
Typing in msgbox keycode under the combobox_keypress event will give you the number of the key you're testing, which you can then place into an if statement to check against like this...
Private Sub Combo1_KeyDown(KeyCode As Integer, Shift As Integer)
If KeyCode <> 32 Then
MsgBox "The key " & Chr(KeyCode) & " was pressed!"