Dim MouseIsDown As Boolean = False
'(...)
Private Sub do_mouseDown(ByVal sender As RectangleShape, ByVal e As _
  MouseEventArgs) Handles Rectangleshape.MouseDown
  MouseIsDown = True
  RunLoop()
End Sub
 
Private Sub do_mouseUp(ByVal sender As RectangleShape, ByVal e As _
  MouseEventArgs) Handles Rectangleshape.MouseUp
  MouseIsDown = False
End Sub
 
Private Sub RunLoop()
  While MouseIsDown
    'Schleife
  End While
End Sub

  Private mIsPressed As Boolean
    Private mPosition As Point
 
    Private Sub PictureBox_Paint(ByVal sender As System.Object, ByVal e As _
      System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint
        e.Graphics.DrawRectangle(Pens.Black, New Rectangle(mPosition, New Size( _
        10, 10)))
    End Sub
 
    Private Sub PictureBox1_MouseDown(ByVal sender As System.Object, ByVal e As _
      System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseDown
        If e.Button = Windows.Forms.MouseButtons.Left Then
            mIsPressed = True
            mPosition = e.Location
            PictureBox1.Invalidate()
        End If
    End Sub
 
    Private Sub PictureBox1_MouseMove(ByVal sender As System.Object, ByVal e As _
      System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseMove
        If mIsPressed Then
            mPosition = e.Location
            PictureBox1.Invalidate()
        End If
    End Sub
 
    Private Sub PictureBox1_MouseUp(ByVal sender As System.Object, ByVal e As _
      System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseUp
        If e.Button = Windows.Forms.MouseButtons.Left Then
            mPosition = e.Location
            PictureBox1.Invalidate()
            mIsPressed = False
        End If
    End Sub