spreadsheet

Hi Everyone.

I'm wondering if you can give me some pointers. Im very new to the drupal world but am blown away so far! however i dont have as much time as i would like to for a real good explore. I want to make a spreadsheet type site - at least a site with logins for individuals who can make balance profiles , comparable tables etc (lets say somebody wants to have an online spreadsheet of their cost/revenue). Can somebody point me in the direction of a few good modules and a way to compare numbers in separate fields using CCK.

I only need high level pointers. Thanks in advance

Regards

Nic