I use case comments for working on Client Service cases

I would like to better track time spent working on cases (preferably by day)

I've created a custom object called "Comment Time Tracking" and associated a custom field called HoursSpent

When I add a case comment, I want to be able to update the HoursSpent field in the custom object.

Any idea's on how to do this?

There are triggers related to 'Case Comments'. Is it possible to do this with a trigger or perhaps a workflow rule?

If so, what would it look like and where could I get the HoursSpent information from the user?

Is it possible to popup a window and request the information when they add a comment?