looping combo box items in vb.net

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


        Dim st As Integer
        Dim storenumber As Integer
        ' storenumber = ComboBox1.SelectedValue

        storenumber = CType(ComboBox1.SelectedValue.ToString(), Integer)

     

         For st = 0 To ComboBox1.Items.Count - 1
            Try
                Dim cnx As OdbcConnection
                Dim dt As New DataTable
                Dim dt1 As New DataTable
                Dim da As New OdbcDataAdapter
                Dim da1 As New OdbcDataAdapter
                Dim ccmd As OdbcCommand
                Dim ncmd As OdbcCommand
                Dim i As Integer = 0
                Dim cnxstr As String
                Dim CSVFolder As String = "C:\Temp\fpcost_csv"

                Dim cmd As New OleDbCommand
                Dim scmd As New OleDbCommand
                Dim CSVFileName As String = "cshpmxp1_41.csv"

                Dim cs As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Temp\test1.mdb;"
                cnxstr = "Driver={Microsoft Text Driver (*.txt; *.csv)};Dbq=" & CSVFolder & ";"
                cnx = New OdbcConnection(cnxstr)

                Dim datcal As Integer

                ncmd = New OdbcCommand("select distinct (COSDAY) from [INVCOSP0_" & storenumber & ".csv]", cnx)
                scmd.CommandType = CommandType.Text
                da1.SelectCommand = ncmd
                cnx.Open()

                dt1.Clear()
                da1.Fill(dt1)

                DataGridView1.DataSource = dt1
                DataGridView1.Refresh()
                cnx.Close()

                datcal = DBConn(storenumber)

                If datcal = 0 Then
                    ccmd = New OdbcCommand("Select COSDAY,COSMIC,COSFOT,COSPOT from [INVCOSP0_" & storenumber & ".csv]", cnx)
                Else
                    ccmd = New OdbcCommand("Select COSDAY,COSMIC,COSFOT,COSPOT from [INVCOSP0_" & storenumber & ".csv] where COSDAY > " & datcal, cnx)
                End If

                cmd.CommandType = CommandType.Text

                da.SelectCommand = ccmd
                cnx.Open()
                dt.Clear()
                da.Fill(dt)

                DataGridView2.DataSource = dt
                DataGridView2.Refresh()
                cnx.Close()


                Dim dd As String
                Dim con As OleDbConnection = New OleDbConnection(cs)
                con.Open()
                Do While i < DataGridView2.RowCount - 1
                    storenumber = CType(ComboBox1.SelectedValue.ToString(), Integer)
                    
                    dd = Mid(DataGridView2.Item(0, i).Value, 5, 2) & "/" & Mid(DataGridView2.Item(0, i).Value, 7, 2) & "/" & Mid(DataGridView2.Item(0, i).Value, 1, 4)

                    Sql = "update test set fcost= " & DataGridView2.Item(2, i).Value & ", pcost=" & DataGridView2.Item(3, i).Value & " where bday=#" & CDate(dd) & "# and strno=" & storenumber & " and mcode= " & DataGridView2.Item(1, i).Value & " "




                    cmd = New OleDbCommand(Sql, con)
                    cmd.ExecuteNonQuery()

                    i = i + 1
                Loop

                
                cmd.Dispose()
                con.Close()



            Catch ex As Exception
                MessageBox.Show(ex.Message, "Store : " & st)
            End Try
        Next

        MsgBox("The Record is Updated", MsgBoxStyle.OkOnly, "Confirmation")


    End Sub