Populating One Dropdownlist with selection of other DropDown

Hi,     I am trying to Populating One Dropdownlist with selection of other DropDownlist control .
can't understand what is goin wrong..coz nothing is happening , just first is working well, i.e 1st Dropdown is binding data sucessfully but 2nd part isn't working...plz help...




  Here's my code...


 Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        If Not IsPostBack Then
            cn.Open()
            boundDp()
            cn.Close()
        End If
    End Sub





Public Sub boundDp()


        cmd.Connection = cn
        cmd.CommandText = "Select * From Acct_Sum"
        Dim da As New SqlDataAdapter(cmd)
        Dim dt As New DataTable
        da.Fill(dt)
        DPA1.DataSource = dt
        DPA1.DataTextField = "Loan_code"
        DPA1.DataValueField = "Loan_code"
        DPA1.DataBind()
        DPA1.Items.Insert(0, "Select Item Here")
    End Sub







Public Sub Shw_data()
        cmd.Connection = cn
        cmd.CommandText = "Select * From Acct_Sum Where Loan_code=@Loan_code"
        cmd.Parameters.AddWithValue("@Loan_code", DPA1.SelectedItem.Value)
        Dim dr As SqlDataReader
        dr = cmd.ExecuteReader
        If dr.HasRows Then
            dr.Read()
            TextBox1.Text = dr.Item("Bor_Name").ToString
            TextBox2.Text = dr.Item("coBor_Name").ToString
        End If


    End Sub







Public Sub shw_data2()
        cmd.Connection = cn
        cmd.CommandText = "Select Loan_code From Acct_Sum2 Where Loan_code=@Loan_code"
        cmd.Parameters.AddWithValue("@Loan_code", DPA2.SelectedItem.Value)
        Dim da As New SqlDataAdapter(cmd)
        Dim dt As New DataTable
        da.Fill(dt)
        DPA2.DataSource = dt
        'DPA2.DataTextField = "chk_Num"
        DPA2.DataValueField = "Loan_code"
        DPA2.DataBind()
        DPA2.Items.Insert(0, "Select Sub Item")




    End Sub





Private Sub DPA2_SelectedIndexChanged(sender As Object, e As EventArgs) Handles DPA2.SelectedIndexChanged
        cn.Open()
       
        shw_data2()
        cn.Close()
    End Sub



Note...I have two tables...Acct_Sum and Acct_Sum2 with Unique ID=Loan_code

Thnx....