Searching on an Attributes Substring

Hello,

I know that most DBMS have the SUBSTRING function that allows you to  
search substrings.  I have an attribute that is an NSString and would  
like to search on a substring of that attribute as part of a fetch  
specification.  Is this possible using EOModeler or manually building  
the fetch specification?  Is this possible or is using the SUBSTRING  
function in raw SQL the way to go?

Regards,
Jeff