In your user control (WebUserControl1.ascx) you may have a Button1 with a click handler that acts like so:
Event Button1Click(ByVal button As Button)
Private Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
RaiseEvent Button1Click(sender)
End Sub
And you can then dynamically attach an EventHandler to this in the parent control like so:
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Dim buttonControl As WebUserControl1 = LoadControl("WebUserControl1.ascx")
AddHandler buttonControl.Button1Click, AddressOf ControlEventHandler
End Sub
Private Sub ControlEventHandler(ByVal ctl As Control)
'We now have access to this control's properties
End Sub