Public Class UserControl1 '// grössere UC
    Inherits System.Windows.Forms.UserControl
    Public Event MyEvent As EventHandler
    Sub test()
        RaiseEvent MyEvent(Me, New EventArgs)
    End Sub
End Class
' ...
Public Class UserControl2 '// kleinere UC
    Inherits UserControl
    Public SetEvent As EventHandler
    Sub test()
        SetEvent.Invoke(Me, New EventArgs)
    End Sub
End Class

    Dim WithEvents u1 As New UserControl1
    Dim WithEvents u2 As New UserControl2
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        u1.test()
        u2.SetEvent = New EventHandler(AddressOf u1_MyEvent)
        u2.test()
    End Sub
    Private Sub u1_MyEvent(ByVal sender As Object, ByVal e As System.EventArgs) _
      Handles u1.MyEvent
        MessageBox.Show(sender.ToString)
    End Sub