How to get my puppy to "go" outside at work.?

I have a 3 mth old Chihuahua/Dachshund. He pees and (mostly) poops outside at home--I take him out often enough. He comes to work with me daily and he'll pee outside, but poops in other people's offices even though I've just taken him out. He doesn't seem to realize he can poop here outside. At home he likes to go in the rocks bordering my house or in leaves. How can I get him to "go" here at work? Do I need to bring some of his poop from home and put it around the area I want him to go in? We stay outside for a while and then he'll come in and have an accident in someone's office. He used to go on pee pads but he's forgetting to go on those too. Any help?