Brauche hilfe bei zahlen konvertieren y.y

MsgBox(0,"Zahl mit Tausenderpunkt", _StringAddThousandsSep(1000000000))

; #FUNCTION# ====================================================================================================================
; Name...........: _StringAddThousandsSep
; Description ...: Returns the original numbered string with the Thousands delimiter inserted.
; Syntax.........: _StringAddThousandsSep($sString[, $sThousands = -1[, $sDecimal = -1]])
; Parameters ....: $sString - The string to be converted.
; $sThousands - Optional: The Thousands delimiter
; $sDecimal - Optional: The decimal delimiter
; Return values .: Success - The string with Thousands delimiter added.
; Author ........: SmOke_N (orignal _StringAddComma
; Modified.......: Valik (complete re-write, new function name)
; Remarks .......:
; Related .......:
; Link ..........;
; Example .......; Yes
; ===============================================================================================================================
Func _StringAddThousandsSep($sString, $sThousands = -1, $sDecimal = -1)
Local $sResult = "" ; Force string
Local $rKey = "HKCU\Control Panel\International"
If $sDecimal = -1 Then $sDecimal = RegRead($rKey, "sDecimal")
If $sThousands = -1 Then $sThousands = RegRead($rKey, "sThousand")
Local $aNumber = StringRegExp($sString, "(\D?\d+)\D?(\d*)", 1) ; This one works for negatives.
If UBound($aNumber) = 2 Then
Local $sLeft = $aNumber[0]
While StringLen($sLeft)
$sResult = $sThousands & StringRight($sLeft, 3) & $sResult
$sLeft = StringTrimRight($sLeft, 3)
WEnd
$sResult = StringTrimLeft($sResult, StringLen($sThousands)) ; Strip leading thousands separator
If $aNumber[1] <> "" Then $sResult &= $sDecimal & $aNumber[1]
EndIf
Return $sResult
EndFunc ;==>_StringAddThousandsSep