apache responce time for each request

["lists user" <suppressed>]

hello members,

We run a video playing site. For each movie, we want to record its played time.
( for example, client A watched movie A for 30 minutes, client B
watched movie B for 2 hours).
So I think for each requested movie, it's maybe possible to get
apache's responce time by modperl.
But how can I do it from the start? please guide me.

Thanks always!

--jen