A custom search function requires that you implement a
search function handler and create a search function definition, as
shown in the following code examples. Also included is an example
for running a custom search function.
Note: 
You cannot use custom search functions in a stored search.
You can use these functions only in ad hoc or background searches.
You cannot use custom search functions in a stored search.
You can use these functions only in ad hoc or background searches.