รบกวนท่านผู้รู้เกี่ยวกับเรื่องฐานข้อมูล sql server 2005 เขียนใน vb 2008 ครับ

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        strSql = "Delete From CheckChem"

        With Comm
            .CommandText = strSql
            .CommandType = CommandType.Text
            .Connection = Conn
            .ExecuteNonQuery()
        End With

        strSql = "Insert Into CheckChem ( IdChem, Chemquantity2 ) SELECT BringChem.BringChemId, " & _
                "Sum(ChemAmountBring) AS SumOfChemAmountBring From BringChem " & _
                "WHERE(((Month([BringChemDate])) = " & ComboBox1.SelectedIndex + 1 & _
                ") And ((Year([BringChemDate])) = " & Year(Now) - 543 & ")) GROUP BY BringChem.BringChemId"
        [color=yellow]'ช่วยแก้ where ให้ทีครับ
        '"WHERE(((Month([BringChemDate])) = " & ComboBox1.SelectedIndex + 1 & _
        '") And ((Year([BringChemDate])) = " & Year(Now) - 543 & ")) GROUP BY BringChem.BringChemId"

        With Comm
            .CommandText = strSql
            .CommandType = CommandType.Text
            .Connection = Conn
            .ExecuteNonQuery()
        End With

        strSql = "Select Chemical.ChemId AS รหัสสารเคมี, Chemical.ChemName AS ชื่อสารเคมี, " & _
                "Chemical.ChemUnit AS หน่วยนับ, Sum(IIf(IsNull([Chemquantity2]),0,[Chemquantity2])) " & _
                "AS จำนวน From Chemical LEFT JOIN CheckChem ON Chemical.ChemId = " & _
                "CheckChem.IdChem Group By Chemical.ChemId, Chemical.ChemName, " & _
                "Chemical.ChemUnit"
        [color=yellow]'ช่วยแก้ sum ให้ทีครับ
        'Sum(IIf(IsNull([Chemquantity2]),0,[Chemquantity2]))

        DA.SelectCommand.CommandText = strSql
        DA.Fill(DS, "SumChemBring")
        DS.Tables("SumChemBring").Clear()
        DA.Fill(DS, "SumChemBring")

        DataGridView1.DataSource = DS.Tables("SumChemBring")
        DataGridView1.ReadOnly = True
    End Sub