HeyTom,
A couple of changes needed:
#include <Array.au3>
Global $aArray[][] = [["Tom", "AA", "-"], _
["Tom", "AA", "+"], _
["Tom", "BB", "+"], _
["Tom", "CC", "+"], _
["Tom", "DD", "-"], _
["Tom", "DD", "-"], _
["Tom", "DD", "+"], _
["Tom", "EE", "+"]]
For $i = UBound($aArray) - 1 To 1 Step -1
; Read line
$sCurrent = $aArray[$i][1]
; Look for earlier duplicates
For $j = $i - 1 To 0 Step -1
If $aArray[$j][1] == $sCurrent Then
$aArray[$j][1] = ""
Else
ExitLoop
EndIf
Next
$i = $j + 1
;_ArrayDisplay($aArray, $i & " - " & $j, Default, 8)
Next
_ArrayDisplay($aArray, "Ended", Default, 8)
Over to you to spot the differences!
M23