You can sue him for tortious, or wrongful, intereference with economic advantage (and possibly also for defamation, if he making untrue but negative or unharmful factual claims or allegations about you or your business to other people). That suit can be brought on an "emergent" (think: "urgent" or "emergency") basis to get into court faster, and you can also seek an "Order to Show Cause" barring him from doing this on a temporary basis while seeking a permanent "injunction" or court order barring him from doing this ever again, and also seek monetary compensation (e.g. if you have lost sales or business). Bring a lawsuit on an emergent basis is more complex than filing a lawsuit along the regular procedure or timeline, and seeking court orders is more complex than seeking only money; you are strongly advised to retain an attorney to help you.