I am trying to programmatically add rows of data to a table web control
in VS2005.  I am getting the data from 2 drop-down controls and 2
text-boxes.  The code below is executed when I click on the "add"
button.  The code is pretty much lifted from an example on MSDN.

Problem:

The first time I try to add a row, it works fine. But when I try to add
another row, it simply overwrites the first.  I need to add new row
every time the user clicks the 'add' button.

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Protected Sub btnProdAdd_Click(ByVal sender As Object, ByVal e As
System.EventArgs) Handles btnProdAdd.Click

        Dim tr As New TableRow()

        Dim cellGrade As New TableCell()
        cellGrade.Text = cboGrade.SelectedValue.ToString
        tr.Cells.Add(cellGrade)

        Dim cellStrips As New TableCell()
        cellStrips.Text = cboStrips.SelectedValue.ToString
        tr.Cells.Add(cellStrips)

        Dim cellYards As New TableCell()
        cellYards.Text = txtYards.Text.ToString
        tr.Cells.Add(cellYards)

        Dim cellScrap As New TableCell()
        cellScrap.Text = txtScrap.Text.ToString
        tr.Cells.Add(cellScrap)

        tblProd.Rows.Add(tr)

    End Sub