[TYPO3-english] Adding a custom language to Backend/Frontend

[Bert Hiddink [BENDOO e-work solutions]]

Hello,

I am looking for a way to add an extra, custom language to a TYPO3 
installation, that is, I need add Spanish (Colombia) on top of the 
spanish language which is available per default in backend and frontend.

Is this possible? If yes, is there a how-to/tutorial somewhere?

Thanks in advance!

Bert Hiddink