การกำหนดค่า combobox และการแสดง DataGridView ได้โปรดช่วยผมหน่อยนะครับพี่ๆ

Imports System.Data
Imports System.Data.OleDb

Public Class FormHistory
    Private _dataset As DataSet
    Private _conn As OleDbConnection
    Private _cmd As OleDbCommand
    Private _adapter As OleDbDataAdapter

    Private Sub FormHistory_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        _conn = New OleDbConnection(_conStr)
        _conn.Open()


        Dim sql As String = "SELECT * FROM Customers"
        _cmd = New OleDbCommand(sql, _conn)
        Dim reader As OleDbDataReader = _cmd.ExecuteReader()


        While reader.Read()
            CmbCust.Items.Add(reader("CustomerName"))
        End While

        sql = "SELECT * FROM Orders"
        _cmd = New OleDbCommand(sql, _conn)
        reader = _cmd.ExecuteReader()


        While reader.Read
            Cmbmonth.Items.Add(reader("OrderedDate"))
        End While


        CmbCust.SelectedIndex = 0
        Cmbmonth.SelectedIndex = 0

    End Sub

Private Sub ShowOrders()
Dim sql As String
        sql = "SELECT * FROM Orders WHERE CustomerName = @cust"
        _cmd = New OleDbCommand(sql, _conn)
        _cmd.Parameters.AddWithValue("cust", CmbCust.SelectedItem)
        sql = "SELECT * FROM Orders WHERE OrderedDate = @orde"
        _cmd = New OleDbCommand(sql, _conn)
        _cmd.Parameters.AddWithValue("orde", Cmbmonth.SelectedItem)
        _adapter = New OleDbDataAdapter(_cmd)
        _dataset = New DataSet()

        _adapter.Fill(_dataset, "ord")
End sub

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

    End Sub