I put the following code in the MouseDown event for the combo box. The text of the item selected is not available "yet" so I set a "pending" variable so the AfterUpdate of the receiving control can take the pending action at that time.
Not sure this is the most appropriate approach but 2017 is rapidly approaching and this item needs to get done........
Code:
Private Sub cboDescriptions_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)
'========================================================================================
' See if control key down at time of selection.
'========================================================================================
If (Shift And acCtrlMask) Then bolDFltPending = True
End Sub