Yes, a confidentiality agreement will help: such agreements are enforceable. You need to get them to sign the agreement before you disclose anything to them--the agreement will not cover pre-execution/signing disclosures. The best way to get a good agreement is to hire a lawyer to draft one for you: most attorneys will be able to draft a very solid, enforceable confidentiality/nondisclosure agreement for $300 - $500, and if your system isn't worth paying that amount protect it, it's probably not worth worrying about disclosures or breach of confidentiality.