Need help on ObjectDataSource control...

Hi,
Is there a way to programmatically call the ObjectDataSource control based on certain selection made in a dropdownlist? Please see code below. When the option with value "kickass" is selected from dropdownlist "ddlMovieCategory", I want to display another dropdownlist for user to select.  All other options will just call the ObjectDataSource (id="srcMovies").  Please provide sample code.

Thanks very much in advance!

Web Form Code:
    <form id="form1" runat="server">
	<div>
    Please select a movie category: 
    <asp:DropDownList 
    ID="ddlMovieCategory" 
    DataTextField="Name" 
    DataValueField="Id" 
    AutoPostBack="true" 
    OnSelectedIndexChanged="ddlMovieCategory_SelectedIndexChanged"
    Runat="server" /> 
 
    <asp:DataList 
        ID="dlMovies" CssClass="dataView" 
        DataSourceID="srcMovies"
        Runat="server">
        <ItemTemplate>
        <h4><%#Eval("MovieTitle")%></h4>
        <%#Eval("MovieDesc")%><br />
		<%#Eval("MoveRating")%>
        </ItemTemplate>
    </asp:DataList>        
        
    <asp:ObjectDataSource
        id="srcMovies"
        TypeName="MovieCategories"
        SelectMethod="GetMovies"
        Runat="server">
        <SelectParameters>
        <asp:ControlParameter
            Name="CategoryId"
            ControlID="ddlMovieCategory" />
       </SelectParameters>
    </asp:ObjectDataSource>
    </div>
    </form>
 
Code-Behind:
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            // Call to the function to populate dropdownlist from xml
            PopulateDDLFromXMLFile();
        }
    }
	
    // Populates the dropdownlist from xml file
    private void PopulateDDLFromXMLFile()
    {
        DataSet ds = new DataSet();
        ds.ReadXml(MapPath("MovieCategories.xml"));
 
        // Get the dataview of table "Category", which is default table name
        DataView dv = ds.Tables["Category"].DefaultView;
        // Or we can use:
        // DataView dv = ds.Tables[0].DefaultView;
 
        // Now sort the DataView vy column name "Name"
        dv.Sort = "Name";
 
        // Now define datatext field and datavalue field of dropdownlist
        ddlMovieCategory.DataTextField = "Name";
        ddlMovieCategory.DataValueField = "ID";
 
        // Now bind the dropdownlist to the dataview
        ddlMovieCategory.DataSource = dv;
        ddlMovieCategory.DataBind();
    }
    protected void ddlMovieCategory_SelectedIndexChanged(object sender, EventArgs e)
    {
        //do something here
    }
 
XML File That Populates Dropdown:
<?xml version="1.0" encoding="utf-8" ?>
<Categories>
  <Category>
    <ID></ID>
    <Name></Name>
  </Category>
  <Category>
    <ID>love</ID>
    <Name>Romance</Name>
  </Category>  
  <Category>
    <ID>kickass</ID>
    <Name>Action</Name>
  </Category>
  <Category>
    <ID>adventure</ID>
    <Name>Adventure</Name>
  </Category>
  <Category>
    <ID>drama</ID>
    <Name>Drama</Name>
  </Category>
  <Category>
    <ID>horror</ID>
    <Name>Horror</Name>
  </Category>
  <Category>
    <ID>scary</ID>
    <Name>Thriller</Name>
  </Category>
</Categories>

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