Redmine

I really need a better way to track when issues last changed state. We have dates for Created and Updated - but in many cases an issue may be modified multiple times without progressing. For example at the end of each month all tasks that are assigned get updated to the new sprint month. People may also add comments or reassign tasks around the team - handing them back and forth. What I need to know is which tasks have not materially progressed the longest.
Another use is knowing for sure when tasks were closed (if they are closed). You generally assume that there have been no updates since a task was closed, but sometimes I find myself cleaning up categories, or making other changes that affect old closed tasks, and all their updated dates change. This breaks my statistics and spoils the integrity of Redmine as an issue database, as well as making my reports innaccurate.

What I would like is an additional field 'DateStatusChanged' which is updated every time an issue changes state and not otherwise.