Edit: read that completely wrong.
Looping through checkbox controls:
Code:
Dim ctl As Control
Dim strListbox as String
For Each ctl In Me.Controls
If ctl.ControlType = acCheckBox Then
If ctl.Value <> True Then
strListbox = strListbox & ";" & ctl.name
End If
End If
Next ctl
strListbox = Mid(strListbox, 2)
me.myListbox = strListbox
The code above adds the name of the unchecked checkbox control to a listbox called myListbox.
OR...
You could set the value of each checkbox as a unique numerical value. Then have them add up. With a lot of math you should be able to get the running total and determine which ones aren't checked right away. I think there are 225 combinations if you have 15 checkboxes.