[TYPO3] What typo3 can do without write my own code

[Typo3 n00b]

I read a lot article and site about typo3, you can do all with it.
But I want to figure out what I can do with typo3+extension without 
write my own extension or php code.
I read is possible to make oscommerce site with an extension, how many 
things are possible with extension support?

For example I need to make for a maketing company. In this site I need 
to put a personal area for the Agents where they have the list of 
appointments of the day updated by others person ( who take the 
appointment for the agents by the phone )

It's possible to make something like this without too many problems?

Thanks to all

p.s. I started 3 weeks ago to learn typo3.