Find page number of cell - speed up code

Dear all,

I found this great (well, somewhat) piece of code, but it's very slow. Does anyone have an idea how to speed it up?

I found it at: http://www.mcgimpsey.com/excel/udfs/pagenumber.html

Here's the code:

   '******************************************************
   'Purpose: Display the page number a cell will be printed on
   'Inputs:  target The cell of interest
   '         nStart The starting page number
   'Returns: The page number of the target cell. Returns
   '         #Ref! if there's an error

   '******************************************************
      Public Function PageNumber( _
                Optional ByRef target As Excel.Range, _
                Optional ByVal nStart As Long = 1&) As Variant
        Dim pbHorizontal As HPageBreak
        Dim pbVertical As VPageBreak
        Dim nHorizontalPageBreaks As Long
        Dim nPageNumber As Long
        Dim nVerticalPageBreaks As Long
        Dim nRow As Long
        Dim nCol As Long
        
        On Error GoTo ErrHandler
        Application.Volatile
        If target Is Nothing Then _
            Set target = Application.Caller
        With target
            nRow = .Row
            nCol = .Column
            With .Parent
                If .PageSetup.Order = xlDownThenOver Then
                    nHorizontalPageBreaks = .HPageBreaks.Count + 1&
                    nVerticalPageBreaks = 1&
                Else
                    nHorizontalPageBreaks = 1&
                    nVerticalPageBreaks = .VPageBreaks.Count + 1&
                End If
                nPageNumber = nStart
                For Each pbHorizontal In .HPageBreaks
                    If pbHorizontal.Location.Row > nRow Then Exit For
                    nPageNumber = nPageNumber + nVerticalPageBreaks
                Next pbHorizontal
                For Each pbVertical In .VPageBreaks
                    If pbVertical.Location.Column > nCol Then Exit For
                    nPageNumber = nPageNumber + nHorizontalPageBreaks
                Next pbVertical
            End With
        End With
        PageNumber = nPageNumber
    ResumeHere:
        Exit Function
    ErrHandler:
        'Could use much more error handling...!
        PageNumber = CVErr(xlErrRef)
        Resume ResumeHere
    End Function