Adding extender dynamically during partial rendering

Ok, so I want to dynamically add a textbox and calendar extender when asked.  This is a result of a specific button click within an update panel.

Action Steps;

1. Page Rendered 
2. Item Selected [triggering updatepanel postback]
3. programmatically add textbox and extender

Private Sub CreateSingleDateControl(ByVal rItem As ReportItem, ByVal ParameterIndex As Integer, ByVal toReturn As Panel)
        Dim sdate As New TextBox
        Dim popup As New AjaxControlToolkit.CalendarExtender
        sdate.ID = rItem.ParameterNames(ParameterIndex)
        popup.TargetControlID = sdate.ID
        toReturn.Controls.Add(sdate)
        toReturn.Controls.Add(popup)
    End Sub

Unfortunately, while the control is rendered on the page it appears that the extender is not (the javascript).  I have added the same 'control' outside of the update panel on first load to ensure that the toolkit is functional and it works fine.

Suggestions?

Steve