Hours

It was suggested for an add-in some time ago. It is technically easy to do once you define what you mean by "build a model" and "editing" precisely. What I can propose to do is: accumulate in document custom properties:

1) total time the document is active (i.e the one with the focus) 2) total time with sketch open 3) total time spent on rebuilds enough ? more ?

Philippe Guglielmetti -

You probably need to use different billing rates. Idle time? Possibly by customer account too. Computervision used to have an accounting function (if enabled) on CADDS-III & IV on the CGOS platform to do this.

BTW, Licom Systems (AlphaCad & AlphaCam) is using a scheme (optional) where the licence to execute is over the net from their offices (cuts way down on piracy and makes light use much more affordable for some) via the NEt, billed on a per-hour basis.

Something like this might make 3rd party apps more marketable. They can get it free but pay per use ... if they don't use it they don't need to pay for it. If it's real handy the "seller" makes money. And such "sales" need not be made one by one by each vendor ..

Just a thought.