Cascade in MDI

Question

Hi, I have problem with laying window cascade in C# .Net. I find only code: this.LayoutMdi(System.Windows.Forms.MdiLayout.Cascade); I call it in click menuItem. It causes that all open window are cascade, even this drop by user. I want to effect how Exel. So when user drop window it must stay on place, and If user close window, new window must open on first free place. I think that I must give in good place this code. Can You help me? I wait on Your notes, Asia