Setup to share internet connection using directional antenneas

I want to share an internet connection between 2 computers, one is in a building located where the router connected to the internet is, the second computer is in another building located about 250 feet from the first.

I have a D-link wireless G router where the internet source is, I'm wondering what kind of antennas (directional) and routers I need to make this work.
I've read posts on the net but do not understand which antenna would be used.

Any help and suggestions would be appreciated