Interact with UserControl on MasterPage

I do not have the code available to post; however, I am having issues interacting with a user-control that is on a Master Page from the (aspx) host-page. The user control consists of a gridview with three columns and it’s bound to data from a database. This all works as expected.  The first column is a Select column. When the user clicks the select column the Gridview1.SelectedValue is past to the host-page into a SqlDatesource Selecting event as  e.command.Paramater("@ID") in order to bind and populate another gridview; however the host page does not refresh until I click the usercontol a second time.  
Public ReadOnly Property Gridview1_SelectedValue() As String
        Get
            Return Gridview1.SelectedValue
        End Get
    End Property
...