Add search by google/yahoo to search engine

Hi all, I've read so many posts but i didn't see any post mention about my problem. So I created a new post.
I want to add a field, can be drop down list to my search engine so user can chose to search within my website or search by google or yahoo.
If anybody know how to do, Pls share with me. Thank you very much..... very urgent.... pls..... :yes:

This might point you in the correct area Google Search/Adsense

thank you for your fast reply however it is not the one i'm looking for.
What i'm looking for now is the code to add in zen cart code which is enable user to chose search within my site or search by google (yahoo) from the drop down list or can click radio button. Something like the search function in this forum or tutorial where I can chose to search from which categories.
Thanks