Day-Time Wife (1939)

When Jane Norton inadvertently discovers that Ken, her husband of two years, is dallying with his beautiful secretary, she decides to turn the tables by applying for a job as secretary to philandering architect Barney Dexter, an associate of her husband. Despite cynical advice from her friend Blanche, a three-time divorcée, Jane stays one step ahead of the amorous Dexter and uses Ken's jealousy to get him to renounce his extra-marital indiscretions.