なんでこれだとちゃんと機能を果たして
Private Sub Form1_Activated(sender As Object, e As EventArgs) Handles Me.Activated
Me.TopMost = True
End Sub

これだとﾀﾞﾒなの?
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Me.TopMost = True
End Sub