Criteria as substring?

Criteria as substring?

Hi,
I have a list of names (first + last as a string), and I would like to fetch entries from a form based on that name.
problem is the form has separated fields for first and last name.
I'm looking for something like
EntriesListPerName= (Form[ First_Name in NamesList && Last_Name in NamesList].ID).getall() ;
but currently the "in" criteria is looking for the full string, and not if it contains as sub string (if in the form First_Name is "John" and Last_Name is "Doe" it will not match an element of "John Doe" in the list)

Hope I explained myself correctly, would appreciate help :)

Ravid