Modify course view appereance

Hi everyone! I'm a really newby of Moodle, and I have got a question for all you experts.

I should modify the course view in this way:

for each resource/activity of the course, the size of icons and the size/colours of text depend from number of members that acceded to that resource, in a time interval choosen by user.

Any suggestion of modules, and files involved? I guess ad hoc renderer should be created, and queries to log table... but it's all very confused.

Hope you can help me a litte!

Eleonora