The Horse in the Gray Flannel Suit (1968) on Netflix

Frederick Bolton has to solve two problems. First, his boss has instructed him to come up with a reasonable campaign to promote a new product, a stomach pill named "Aspercel" - by tomorrow. The second problem is Fred's daugther, Helen. She is absolutely fond of horses, takes riding classes and has already had decent success in some competitions. Her biggest wish is to own a horse herself, a dream her father cannot afford at all. Now Fred tries to solve both problems at once by simply combining them: A horse named "Aspercel", ridden by his daugther should bring the name of the pill into the papers and make Helen happy, too. But there's still one more obstacle: Helen and Aspercel of course have to win a few races to make this idea work...