We're Puttin' on the Ritz (1986)

Two employees of a reclusive millionaire, Micki the secretary and Max the chauffeur, decide to attend a society function to which their employer has been invited. In the course of the evening, Max and Micki establish new identities in the world of high society and, while rubbing shoulders with the elite, they uncover a scam that tests their sleuthing skills as much as their social skills.