AutoCAD .NET :: How To Change All Documents Of Tile Mode To 0

I would like to change all the DOCUMENTS of the Tile Mode to 0. But, the following code the Active Document changes only. How can I modify the code?
 
Dim acdc As DocumentCollection = Application.DocumentManager Dim acdoc As Document = acdc.MdiActiveDocument Dim acTile As Integer = Application.GetSystemVariable("TileMode") For Each acdoc In acdc If acTile = 1 Then Application.SetSystemVariable("TILEMODE", 0) End If Next End Sub