Private Sub Form1_Resize(ByVal sender As Object, _
     ByVal e As System.EventArgs) Handles Me.Resize
 
     Static z As Integer
 
     z += 1
 
     If TypeOf sender Is Control Then
        TextBox1.AppendText(CStr(z) & " " & CType(sender, Control).Name & _
          vbNewLine)
     Else
        TextBox1.AppendText(CStr(z) & " " & sender.GetType.Name & vbNewLine)
     End If
End Sub

Public Class SubForm
    Private Sub SubForm_Load(ByVal sender As System.Object, _
        ByVal e As System.EventArgs) Handles MyBase.Load
        Me.Text = "Subform"
        Me.Size = New Size(300, 100)
    End Sub
End Class
 
Public Class StartForm
    Dim mySubform As New SubForm
    Dim WithEvents btn As New Button With {.Text = "Subform", .Parent = Me}
 
    Private Sub StartForm_Load(ByVal sender As System.Object, _
        ByVal e As System.EventArgs) Handles MyBase.Load
        Me.Size = New Size(200, 250)
    End Sub
 
    Private Sub btn_Click(ByVal sender As Object, _
        ByVal e As System.EventArgs) Handles btn.Click
        mySubform.ShowDialog()
    End Sub
End Class