This is a System style constant used by the SalMessageBox function to display a dialog box that suspends ALL application windows until you respond appropriately. You can combine a System style constant with a constant from the Icon style, Response Button Handling style, and Push Button style constant groups (all of which are also named MB_*) using the OR (|) operator. See SalMessageBox Options and SalMessageBox Returns for more information. Value = 0x1000

public const int MB_SystemModal