Extending Options

I would like to extend the Unit Options by a description. (adding a field to the database table named "Long Description")

Eg:

Option:
Name: Mobile Internet
Quantity: 1
Operation: Add
Value: 5.-
Description: We can provide you with a mobile internet USB-Stick for your personal computer

How would I start to extend Rooms - Units - Options in a separate module (as not to interfere with source code of Rooms)

Can anyone give me a hint if this can be done?