Who is using that file?

If you are unable to open a drawing for editing (read-only) because it is in use, and want to find out who has it open, start a new drawing, or go to a drawing you have open and type WHOHAS at the command line. Browse to the drawing file using the file dialog box and double-click the filename (or select the file and click the Open button). A small message box will appear, showing who is using the file, the name of their PC and when it was opened.