Hey guys, I just found a netlist trace and ECO tool, which looks perfect for me. It allows users draw and isolate gates in schematics by just clicking on gate pins. Starting from one cell user has interest in, after several mouse clicking and moving, one circuit appears. Users can move, replace, delete or add gates in the schematics, and can also drag and drop gates from codeview window. By using this tool, debugging is not a problem anymore. And the best thing is, you can try it for free!! Go and take a look [URL]http://www.necosys.com/[/URL]