Private Sub btnTotal_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnTotal.Click

        Try
            Dim totalSum As Integer

            For i As Integer = 0 To ds.Tables(0).Rows.Count - 1
                totalSum += ds.Tables(0).Rows(i).Item("TotalAmount")
            Next

            Label1.Text = "Total : " & totalSum.ToString()
        Catch ex As Exception
            MsgBox(ex.ToString)
        End Try
     
    End Sub

Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        Dim Total As Integer = 0
        For i As Integer = 0 To DataGridView1.RowCount - 1
            If DataGridView1.Rows(i).Cells(1).Value = TextBox1.Text Then
                Total += DataGridView1.Rows(i).Cells(2).Value
            End If
        Next
        If Total = 0 Then
            MessageBox.Show("No Records Found")
        End If
        Label1.Text = Total
    End Sub