Public Class Form3
    Inherits System.Windows.Forms.Form
#Region " Vom Windows Form Designer generierter Code "
#End Region
    Private _IsLoad As Boolean = True
    Public ReadOnly Property IsLoad() As Boolean
        Get
            Return Me._IsLoad
        End Get
    End Property
    Private Sub Form3_Activated(ByVal sender As Object, ByVal e As _
      System.EventArgs) Handles MyBase.Activated
        Me._IsLoad = False
    End Sub
End Class

Dim f As New Form3
f.Show()
While f.IsLoad
  Application.DoEvents()
  Threading.Thread.Sleep(100)
End While
 ' fertig geladen
DEIN_CODE

  Dim f As New Form3
  f.Show()
   While Not ActiveForm Is f
       Application.DoEvents()
       Threading.Thread.Sleep(100)
    End While
 ' fertig geladen
DEIN_CODE