Programatically changing datasource parameters

Hi
 I have a form with a couple of drop down lists and three object data sources. The first drop down list is populated by one data source, and the second drop down list is populated by one of the other two data sources depending on the user's selection from the first list. In my code behind:
        
Dim Org As New Guid(OrgDropDownList.Value.ToString)
If Not Org = Guid.Empty Then
AreaDropDownList.DataSourceID = "AreaObjectDataSource"
AreaObjectDataSource.DataBind()
Else
AreaDropDownList.DataSourceID = "AllAreasObjectDataSource"
AllAreasObjectDataSource.DataBind()
End If
AreaDropDownList.Data ...