Public Class _Interface
    Interface Inter
        Function Init(ByVal f As TabControl) As Boolean
    End Interface
End Class

Public Class UserControl1
    Inherits System.Windows.Forms.UserControl
    Implements _Interface.Inter
 
[Vom Windows forms Designer generierter Code]
 
    Public Function Init(ByVal f As TabControl) As Boolean Implements _
      _Interface.Inter.Init
        f.TabPages.Add(New TabPage("Interface"))
    End Function
End Class

 Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
   System.EventArgs) Handles Button1.Click
        Dim uit As _Interface.Inter
        Dim a As System.Reflection.Assembly = _
        System.Reflection.Assembly.LoadWithPartialName("WindowsApplication4")
        uit = Nothing
        uit = a.CreateInstance("VBSystems.Forms.UserControl1")
        uit.Init(TabControl1)
    End Sub