Hi youtuber, this could do it :
Global $aArray[8][2] = _
[["BCES", "NPEA"], _
["BLES", "NPEB"], _
["BCUS", "NPUA"], _
["BLUS", "NPUB"], _
["BCJS", "NPJA"], _
["BLJM", "NPJB"], _
["BCAS", "NPHA"], _
["BLAS", "NPHB"]]
Global $aID = "BLUS12345", $aID_New = "", $aID_Left = StringLeft($aID, 4)
For $i = 0 To 7
If $aID_Left = $aArray[$i][0] Then
$aID_New = $aArray[$i][1] & StringMid($aID, 5)
ExitLoop
EndIf
Next
If $aID_New <> "" Then
MsgBox(0, "Found", $aID & " => " & $aID_New)
Else
MsgBox(0, "Not Found", "No replacement done")
EndIf
Good luck