Pivot Chart - change with VBA

[Apfel007]

Hi there,
I'm quite new on vba and I try to understand how to change a chart with VBA.

I found this usefull link Dynamic Chart using Pivot Table and VBA - Peltier Tech Blog.

But I don't understand it completely.

Let's have a look on the screenshot:
https://www.dropbox.com/s/dgvl08mggx7ke76/pivot_chart_dynamic.png

In the end I like to recreate a chart by choosing the year number in a combobox. But first I like to understand how to recreate a chart.
Each category should get it's own chart, which compare two years, but I will start with one chart.

What is the starting point to say " use year 2012 + 2013 and category A " and draw the chart line?

Sub UpdateChartFromPivot()
  'update charts on cheet
    Dim rCategories As Range  '??
    Dim rValues As Range ' ??
    
    Dim rYear As Range
    Dim rMonth As Range
    
    Dim pt As PivotTable
    Dim cht As Chart
    Dim iMonth As Long
    
    Dim nMonth As Long 'number of month


    ' Define the Pivot Table   - OK
    'Set pt = ActiveSheet.PivotTables(1)
    Set pt = ActiveSheet.PivotTables("PivotTable2")


    ' Define the Ranges with set!   What RANGE is it?
    Set rValues = pt.DataBodyRange 'Werte felder
        
    'Y in pivot table?
    With pt.RowRange
        Set rCategories = .Offset(2).Resize(.Rows.Count - 2)   '??
    End With
    
    ' Monate !! x achse
    Set rMonth = pt.ColumnRange.Rows(2)


    ' Define the Chart
    'Set cht = ActiveSheet.ChartObjects(1).Chart
    Set cht = ActiveSheet.ChartObjects("Diagramm 1").Chart


    ' How Many Month/Series?
    nMonth = rMonth.Columns.Count ' Anzahl der Monate ->Columns count
    
   '******  this I completely not understand!!!  ************
    ' Remove or Add Series until Chart Has Correct Number
    Select Case cht.SeriesCollection.Count - nMonth
        Case Is > 0
            ' too many: remove excess series
            For iMonth = cht.SeriesCollection.Count To nMonth + 1 Step -1
                cht.SeriesCollection(iMonth).Delete
            Next
        Case Is < 0
            ' too few: add sufficient series
            For iMonth = cht.SeriesCollection.Count + 1 To nMonth
                cht.SeriesCollection.NewSeries
            Next
        Case Else
            ' just right
    End Select


    ' Populate Each Series
    For iMonth = 1 To nMonth
        With cht.SeriesCollection(iMonth)
            '.Name = rMonth.Columns(iMonth ) ' Monate
            '.Values = rValues.Columns(iMonth )
            '.'XValues =  ' Jahreszahlen
            .Name = rMonth.Columns(iMonth)
            .Values = rValues.Columns(iMonth)
            .XValues = rMonth.Columns(iMonth) 'rCategories
            .Border.LineStyle = xlContinuous
        End With
    Next
    
    End Sub

Thanks for your help

Cheers K.