I need to populate the S column. S1 = header string and S2-end = value from the formula. I need to filldown.

I'm doing several test based on the following cone below (I'm think I'm pretty close to the solution).
Sub NewTest()    
    Dim sh As Worksheet
    Dim rng As Range
    Set sh = Sheets("Existing 2W")
    Set rng = Range("S2:S" & Range("S" & Rows.Count).End(xlUp).Row)
    
    Sheets("Existing 2W").Range("S1").Interior.ColorIndex = 3 ' 3 indicates Red Color
    ''''The following two lines are working fine to fill the S2 cell but now I want to fill S2:S
    'Sheets("Existing 2W").Range("S2").Value = WorksheetFunction.Index(Range("Latest_Range"), WorksheetFunction.Match(Left(Right((Sheets("Existing 2W").Range("Z2").Value), 11), 5), Range("LatestLineNo"), 0), 11)
    'Sheets("Existing 2W").Range("S2").Value = Application.Index(Range("Latest_Range"), Application.Match(Left(Right((Sheets("Existing 2W").Range("Z2").Value), 11), 5), Range("LatestLineNo"), 0), 11)
    With sh
        With .Range("S2")
            .FormulaLocal = "=INDEX(Latest_Range;EQUIV(GAUCHE(DROITE(Z2;11);5);LatestLineNo;0);11)"
            .FormulaArray = .Formula
            .AutoFill rng
        End With
    End With
End Sub