Printer Macro to change printers

The macro listed below allows changing printers. I can change from MX880 to MX850 but it wil not change back. It says the MX850 is the active printer and do I want to change to MX850. What is wrong with my code.

If ActivePrinter = "Canon MX850 series Printer" Then
    AlternatePrinter = "Canon MX880 series Printer:"
    Else
    AlternatePrinter = "Canon MX850 Series Printer"
    End If
    userReply = MsgBox("Active printer is " & ActivePrinter & vbCrLf & "Do you want to change this to " & AlternatePrinter & "?", vbYesNo + vbQuestion, "Printer Selection")
    If userReply = vbYes Then
ActivePrinter = AlternatePrinter
    End If
End Sub