Prevent developer from placing a UserControl more than one time in Design Time

Question

I am working on a UserControl and I am looking for a way to prevent developer to place this UserControl more than one time into a form. All this in Design Time. In other words, how can I detect if my UserControl is already placed into ParentForm or not, in Design Time(!!!), and prevent the second placement if there is already one there?

I tried something like this example below... First I am not sure if this is the "correct" way and second I can't find how to remove or stop the placement of UserControl in case there is already one.

Again, all this, in Design Time!!!

Private Sub MyUserControl_Load(sender As Object, e As EventArgs) Handles MyBase.Load 
    Dim _Count As Integer
    Dim _UserControl As MyUserControl
    For Each _UserControl In Me.ParentForm.Controls
        If _UserControl.Name.Contains("MyUserControl") Then
            _Count += 1
        End If
    Next
    If _Count > 1 Then
        MsgBox("Control have been placed.")
    Else
        MsgBox("Control haven't placed yet.")
    End If
End Sub

Answer 1

Finnaly I ended to this...

Private Sub Me_ParentChanged(sender As Object, e As EventArgs) Handles Me.ParentChanged

    Dim _ParentForm = DirectCast(Me.FindForm, Control)
    Dim _ControlName As String

    If _ParentForm IsNot Nothing Then
        For Each _Control As Control In _ParentForm.Controls
            If TypeOf _Control Is MyUserControl AndAlso _Control IsNot Me Then
                Throw New ArgumentOutOfRangeException("", "You can place only one " & _ControlName & " control per form.")
            End If
            _Control = _ParentForm.GetNextControl(_Control, True)
        Next
    End If

End Sub