Did you ever come across "getmac"?
This should send you on your way:
#include <AutoItConstants.au3>
$DSK = Run("getmac", '', '', $STDIN_CHILD + $STDOUT_CHILD)
$begin = TimerInit()
$dif = TimerDiff($begin)
Do
Sleep(100)
$Read = StdoutRead($DSK, False, False)
$Str = StringInStr($Read, 'Physical Address')
If $dif >= 1000 Then
MsgBox(64, 'Error', 'Timeout')
ExitLoop
EndIf
$dif = TimerDiff($begin)
Until $Str <> 0
;MsgBox(64, 'Result', $Read)
$ReadTr = StringTrimLeft(StringStripWS($Read, 8), 105)
$Split = StringSplit($ReadTr, '\Device', 1)
;MsgBox(64, 'Count', $Split[0])
For $s = 1 To $Split[0]
If $s <> $Split[0] Then
MsgBox(64, '', $Split[$s])
EndIf
Next
Note that i only got one MAC address (only one network adapter), so i couldn't adapt the code for multiple, but maybe you can.