Add text input option to dropdown?

Hi Guys,
Is there a way to add a text input (text box) option if someone selects a specific value from a dropdown?

We would like to monitor how people have heard about our company and therefore have added a single dropdown with options to select.
i.e.
Twitter
Facebook
Web
Friend
Other

We would like to add an option for a text box when 'other' is selected to give further details, is this possible?

Hi,

Yes it's possible, you have to create a new custom field in the table "order" if you want this custom field to be displayed in the checkout.
Then create another custom field and restrict the display of this one to the other one. The option is "Display limited to"

Cheers Xavier, that worked a treat!!