Option Explicit
Dim isChart As Boolean ' True = chart added; False = chart deleted
Dim isRent As Boolean ' True = column clustered; False = line markers
Dim isBuy As Boolean ' True = column clustered; False = line markers
Dim isTitle As Boolean ' True = visible; False = hide
Dim isLegend As Boolean ' True = visible; False = hide

' 2.  Implement click event handler for the Chart button. (+20pts)
Sub ButtonChart_Click()

Dim chtObject As ChartObject
Dim cht As Chart
Dim sc As SeriesCollection
Dim ser As Series
Dim topCell As Range

If isChart Then Sheet2.ChartObjects.Delete

Set chtObject = ThisWorkbook.Worksheets("Chart").ChartObjects.Add(Range("D3").Left, Range("D3").Top, Range("D3:M20").Width, Range("M3:M20").Height)
chtObject.Name = "Monthly"
isChart = True

Set cht = chtObject.Chart
Set topCell = Range("A1")

With cht
    .HasLegend = True
    .HasTitle = True
    .ChartTitle.Text = "Monthly Average"
    Set sc = .SeriesCollection
    Set ser = sc.NewSeries
    With ser
        .Name = topCell.Offset(1, 1)
        .XValues = Range(topCell.Offset(2, 0), topCell.Offset(2, 0).End(xlDown))
        .Values = Range(topCell.Offset(2, 1), topCell.Offset(2, 1).End(xlDown))
        .ChartType = xlLineMarkers
        End With
    Set ser = sc.NewSeries
    With ser
        .Name = topCell.Offset(1, 2)
        .Values = Range(topCell.Offset(2, 2), topCell.Offset(2, 2).End(xlDown))
        .ChartType = xlColumnClustered
        .AxisGroup = xlSecondary
    End With
End With