Search for dformd.dll in your Aveva directory and place a copy of this file in your plot (C:\AVEVA\Pdms11.6.SP3\plot) directory. You should then be able to run plot from a DOS command prompt.
Search for dformd.dll in your Aveva directory and place a copy of this file in your plot (C:\AVEVA\Pdms11.6.SP3\plot) directory. You should then be able to run plot from a DOS command prompt.