using new parameter using session condition

I have a session1 parameter set in the select code for my detailsview in my aspx page.  I want to check for a different session2 when the page loads.  If that session2 exists, then use the select parameter using the different session2.  I tried the following code but it is not picking up the new session.  I know the session value is there from posting it to a label.  Can someone advise how to set a different Select parameter in code behind?
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load If Session("subMem") IsNot Nothing Then SqlDataSource1.SelectParameters.Add("@MemId", Session("subMem")) DetailsView1.DataBind() End If End Sub