A noun or noun phrase that follows a preposition is termed the object of the preposition.
Viking obtained no conclusive data for or against life
on Mars--an important reason for sending new probes to
the enigmatic red planet in the near
--Kai Wu, "Artificial Life," SciTech Magazine
Always use the objective case form of pronouns that are objects of prepositions, even when the pronoun follows a coordinating conjunction such as and.
Just between you and I, I think this proposal needs some
Just between you and me, I think this proposal needs
some more work.