How to pop up the message box to alert the user if the printer were not found in the local machine?

Code:
'Add all the available printers to the combo box
For i% = 0 To Printers.Count - 1
    Combo1.AddItem Printers(i%).DeviceName
Next i%

'Display the default printer
For i% = 0 To Combo1.ListCount - 1
If Combo1.List(i%) = Printer.DeviceName Then
Combo1.ListIndex = i%
Exit For
End If
Next i%