Last Of: (naive) Function to find the last instance of a string

' Find the last (sheet index-wise) instance of a string
' search: The text to search for
' firstSheet: The lower bound of sheet index to search
' lastSheet: The upper bound of sheet index to search
'
' Caveat: Assumes search string is unique on sheet
Function LASTOF(search As String, Optional firstSheet As Integer = 0, Optional lastSheet As Integer = -1) As String
    Dim i As Integer
    Dim ls As Integer

    ' If lastSheet wasn't set, use the end of the workbook
    If lastSheet > -1 Then ls = lastSheet Else ls = Application.Worksheets.count

    ' Walk backwards over sheets from ls, stopping at firstSheet
    For i = ls To firstSheet - 1 Step -1
        Dim ws As Excel.Worksheet
        Dim res As Excel.Range
        Dim c As Excel.Range
        Set ws = Application.Worksheets(i)
        ' Search for given search text
        Set res = ws.Cells.Find(What:=search, _
            After:=ws.Cells(1, 1), _
            LookIn:=xlValues, _
            lookAt:=xlPart, _
            SearchOrder:=xlByRows, _
            SearchDirection:=xlNext, _
            MatchCase:=False, _
            MatchByte:=False, _
            SearchFormat:=False)
        ' If found, return address
        If Not res Is Nothing Then
            LASTOF = res.Address(RowAbsolute:=True, _
                ColumnAbsolute:=True, _
                ReferenceStyle:=xlR1C1, _
                External:=True)
            Exit Function
        End If
    Next i
End Function