Custom Search Engine APIs - Custom Search on the fly

You can now create a CSE by simply placing a small piece of tailored code on a page on your site. With that one piece of code, Google's search technology will automatically include in your new CSE all of the sites you have linked to from that page, creating a dynamic, powerful and tailored search experience really quickly. Moreover, your new CSE will update itself periodically to include any new links added to that page.

The link address is: http://googlecustomsearch.blogspot.com/2007/06/custom-search-engine-apis.html