pie chart in ajaxtoolkit with asp.net

Hi,

I am new to pie chart, but i have a pie chart in my aspx page.

<cc1:PieChart ID="PieChart1" runat="server" ChartHeight="300" ChartWidth = "300"
            ChartType="Column" ChartTitleColor="#0E426C" Visible = "true">
         
        </cc1:PieChart>

and from code behind I want to add 4 segment to it:

 Dim ch1 As New AjaxControlToolkit.PieChartValue
        For j = 1 To 4
            PieChart1.PieChartValues.Add(ch1.Category = "test", ch1.Data =j)
        Next

But I keep getting Data error.

any help?

Thanks,