Open stage duration - Leads/Opportunities

Hi all,

I seem to have found lots of guidance on retrospectively measuring stage duration when both the start and end date of a stage/business process flow are known, but what I want is:

A SORTABLE field in a view that shows the duration of an open (Current) stage. (In other words, there is no end date to the stage).

I tried creating a calculated field called Stage Duration that showed daysdiff between start date and NOW(), but it seems that because the NOW element is another calculation, this field cannot be sorted...

Business requirement here is to chase up open stages, and deal with the ones that have been open in that stage for the longest time.

Surely others have this need?

Any suggestions (other than reports!!) gratefully received.

Thanks in advance.

Mark