JdeB, My understanding is that @ERROR is just an internal Au3 Macro for retruncode. A full list of Internal Macros is in the helpfile, and a full test of all of these Macros is done by van_renier availabel at: http://groups.yahoo.com/group/AutoItList/files/AU3/SCRIPTS/ FULL Test of Auto-it Switches and innate variables.zip from Autoit3 help file Macros ====== Read only variables with special values. Similar to the AutoIt v2 "A_DAY" type variables. e.g. @MyDocuments, @StartupCommon Full list: "error", "SEC", "MIN", "HOUR", "MDAY", "MON", "YEAR", "WDAY", "YDAY", "ProgramFilesDir", "CommonFilesDir", "MyDocumentsDir", "AppDataCommonDir", "DesktopCommonDir", "DocumentsCommonDir", "FavoritesCommonDir", "ProgramsCommonDir", "StartMenuCommonDir", "StartupCommonDir", "AppDataDir", "DesktopDir", "FavoritesDir", "ProgramsDir", "StartMenuDir", "StartupDir", "Computername", "WindowsDir", "SystemDir", "SW_HIDE", "SW_MINIMIZE", "SW_MAXIMIZE", "SW_RESTORE", "SW_SHOW", "ScriptFullPath", "ScriptName", "ScriptDir", "WorkingDir", "OSType", "OSVersion", "OSBuild", "OSServicePack", "AutoItVersion", "IPAddress1", "IPAddress2", "IPAddress3", "IPAddress4", "CR", "LF", "CRLF", "DesktopWidth", "DesktopHeight" ======