#include <WinAPI.au3>
#include <WindowsConstants.au3>
#include <Array.au3>

Local $a[] = [_WinAPI_GetSystemMetrics($SM_CMONITORS)] _ ; Number of monitors.



$monitors = _WinAPI_GetSystemMetrics($SM_CMONITORS) ;Save amount of monitors in a Variable


if $monitors = 1 Then
   RegDelete("Computer\HKEY_CURRENT_USER\Control Panel\Desktop", "WallPaper")
   RegWrite("HKEY_CURRENT_USER\Control Panel\Desktop", "WallPaper", "REG_SZ", "C:\Users\User\Desktop\Files\wallpapers\1mon.jpg")

Elseif $monitors = 2 Then
   RegDelete("Computer\HKEY_CURRENT_USER\Control Panel\Desktop", "WallPaper")
   RegWrite("HKEY_CURRENT_USER\Control Panel\Desktop", "WallPaper", "REG_SZ", "C:\Users\Kevin\Desktop\Files\wallpapers\2mon.bmp"
EndIf


Run("commit.bat") ;This applys the changes I made in RegEdit. Content of this file is in the Post.
ConsoleWrite("Wallpaper set for " & $monitors & " Monitors")