Some time ago I started to work on a “graphic meter bar” that could represent a relative generic completion.
As I needed to reference it in different tables, I decided to generalise it so that all the logic would have been in the same table and I could only look-up (through a value) this table externally.
Eventually I didn’t use it at all… 
but perhaps could be useful for somebody:
I also externalised all the elements so that I could play around with different configurations without intervening on the table itself.
Note: Is was intended to work on “number of tasks” or similar but it could easily extended to work with time.
I think it’s quite self-explanatory and there are some basic tests already, but feel free to ask/comment: happy to know.
Cheers.