You mean you want to have a short script that will go through the entered text and chanage exact words to a hrefs? For example your enter "Hi everyone here" and the script will make "hi everyone < a href='nintendo.com.... "?

If so then my only idea how to do this is in php A short script with preg_replace - function that go through entered text and change selected words...
More can be found here.

It's pretty simple so maybe it can help you. If you have any problems feel free to write to me - maybe I can help you with this script