用户控件的问题？（可以加分）

这样一个程序，该如何做成用户控件？
参数主要有三个：左右两个listbox和数据源
控件的值是右边listbox中的项。<body>
    <form id="form1" runat="server">
    <div>
        <table style="width: 472px; height: 176px">
            <tr>
                <td rowspan="3" style="width: 100px">
                    <asp:ListBox ID="L_ListBox" runat="server" DataSourceID="SqlDataSource1" DataTextField="LastName"
                        DataValueField="LastName" Height="100px" Width="150px"></asp:ListBox><asp:SqlDataSource
                            ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:NorthwindConnectionString4 %>"
                            SelectCommand="SELECT [LastName] FROM [Employees]"></asp:SqlDataSource>
                </td>
                <td rowspan="3" style="width: 100px">
                    <table>
                        <tr>
                            <td style="width: 100px">
                                <asp:Button ID="Button1" runat="server" Text=">>" Width="50px" /></td>
                        </tr>
                        <tr>
                            <td style="width: 100px">
                                <asp:Button ID="Button2" runat="server" Text=">>>>" Width="50px" /></td>
                        </tr>
                        <tr>
                            <td style="width: 100px">
                                <asp:Button ID="Button3" runat="server" Text="<<" Width="50px" /></td>
                        </tr>
                        <tr>
                            <td style="width: 100px">
                                <asp:Button ID="Button4" runat="server" Text="<<<<" Width="50px" /></td>
                        </tr>
                    </table>
                </td>
                <td rowspan="3" style="width: 100px">
                    <asp:ListBox ID="R_ListBox" runat="server" Height="100px" Width="150px"></asp:ListBox></td>
            </tr>
            <tr>
            </tr>
            <tr>
            </tr>
        </table>
    
    </div>
    </form>
</body>
-------------以下是vb代码-----------------------------
Partial Class Default4
    Inherits System.Web.UI.Page    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load    End Sub    Protected Sub button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim i, n As Integer
        i = 0
        n = L_ListBox.Items.Count - 1
        While i <= n
            If L_ListBox.Items(i).Selected Then
                R_ListBox.Items.Add(L_ListBox.Items(i))
                L_ListBox.Items.Remove(L_ListBox.Items(i))
                R_ListBox.Items(R_ListBox.Items.Count - 1).Selected = False
                n = n - 1
            Else
                i = i + 1
            End If
        End While
    End Sub    Protected Sub button2_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button2.Click
        Dim i, n As Integer
        i = 0
        n = L_ListBox.Items.Count
        While n > 0
            R_ListBox.Items.Add(L_ListBox.Items(i))
            L_ListBox.Items.Remove(L_ListBox.Items(i))
            n = n - 1
        End While
    End Sub    Protected Sub button3_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button3.Click
        Dim i, n As Integer
        i = 0
        n = R_ListBox.Items.Count - 1
        While i <= n
            If (R_ListBox.Items(i).Selected) Then
                L_ListBox.Items.Add(R_ListBox.Items(i))
                R_ListBox.Items.Remove(R_ListBox.Items(i))
                L_ListBox.Items(L_ListBox.Items.Count - 1).Selected = False
                n = n - 1
            Else
                i = i + 1            End If
        End While
    End Sub    Protected Sub button4_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button4.Click
        Dim i, n As Integer
        i = 0
        n = R_ListBox.Items.Count
        While n > 0
            L_ListBox.Items.Add(R_ListBox.Items(i))
            R_ListBox.Items.Remove(R_ListBox.Items(i))
            n = n - 1
        End While
    End Sub
End Class