Finding last modification of a course

Hi,
I'd like to be able to backup only courses which have been modified last day.
By modified, I mean if any action has been done on this course (adding any activity or resource, adding users to the course, etc.)
Is it possible to get this information ? Where can I find it ?

I saw in the database the field timemodified in the mdl_course table. The problem is that this field is updated only if the "structure" of the course is updated (ie the title or the description), not the content of this.

I hope I've been understandable

Thanks a lot for your answer.