Help creating licence key input box

#include <GUIConstantsEx.au3>

HotKeySet("{BACKSPACE}","_BackSpace")
Global $gui = GUICreate("...",600)
Global $Input = GUICtrlCreateInput("", 8, 150, 584, 35)
    GUICtrlSetLimit($Input,29)
    GUICtrlSetFont($Input,20)
Global $LastInput = ""
GUISetState()
Local $Temp, $LenPart = 5
While 1
    If $LastInput <> GUICtrlRead($Input) Then
        $LastInput = GUICtrlRead($Input)
        If StringLen($LastInput) = $LenPart Then
            $LastInput &= "-"
        Else
            $Temp = StringSplit($LastInput,"-")
            If $Temp[$Temp[0]] <> "" And StringLen($Temp[$Temp[0]]) >= $LenPart And StringLen(GUICtrlRead($Input)) < 29 Then
                $LastInput &= "-"
            EndIf
        EndIf
        GUICtrlSetData($Input,$LastInput)
    EndIf
    $Msg = GUIGetMsg()
    Switch $Msg
        Case $GUI_EVENT_CLOSE
            Exit

    EndSwitch
WEnd

Func _BackSpace()
    If Not WinActive($gui) Then Return 0
    If StringRight($LastInput,1) = "-" Then
        Return GUICtrlSetData($Input,StringLeft($LastInput,StringLen($LastInput)-2))
    Else
        Return GUICtrlSetData($Input,StringLeft($LastInput,StringLen($LastInput)-1))
    EndIf
EndFunc