Как в HEX строке поменять байты местами, и записать результат в файл?

#include <EditConstants.au3>
#include <GUIConstants.au3>
#include <string.au3>
$Save_file = 'Hex.txt'
$File = "cfunction.txt"
$HEX = _StringToHEX(FileRead($File,-1))
$main = GUICreate("String To Hex", 520, 550)
$Text = GUICtrlCreateEdit("",10,10,500,500)
GUICtrlSetData(-1,$HEX & @CRLF)
DllCall('User32.dll', 'long', 'AnimateWindow', 'hwnd', $main, 'long', 800, 'long', 0x10)
$Save = GUICtrlCreateButton("Save",10,520,50,20)
$Close = GUICtrlCreateButton("Close",70,520,50,20)
$About = GUICtrlCreateButton("About",130,520,50,20)
GUISetState()

While 1
  $msg = GUIGetMsg()
    Switch $msg
	Case $msg = 0
	Case $Save
		FileWrite($Save_file,$HEX)
    Case $About
		MsgBox(0,"test","test" & @CRLF & "test")
	Case $GUI_EVENT_CLOSE, $Close
		 DllCall('User32.dll', 'long', 'AnimateWindow', 'hwnd', $main, 'long', 800, 'long', 0x10 + 0x10000)
         ExitLoop	
EndSwitch
WEnd

$sData = '4D525047434D41501040'
$bData = Binary('0x' & $sData)
$tByte = DllStructCreate('byte[' & (BinaryLen($bData) - Mod(BinaryLen($bData), 2)) & ']')
$tWord = DllStructCreate('word[' & (DllStructGetSize($tByte) / 2) & ']', DllStructGetPtr($tByte))
DllStructSetData($tByte, 1, $bData)
For $i = 1 To DllStructGetSize($tWord) / 2
	ConsoleWrite(Hex(DllStructGetData($tWord, 1, $i), 4))
Next
ConsoleWrite(@CR)