How can I encourage my Dachshund to 'do his business' on a short walk?

My 3 year old COMPLETELY housebroken dash is VERY stubborn and sometimes refuses to do a BM unless I take him on a really LONG walk. It's like he knows that when he does, we are going back home. The problem is that he is under heartworm treatment, and not supposed to take long walks, just enough to potty and come back in. Sometimes he will do it, and other times he just pees, yet I have found where he went poop after we got in. This is very unusual, since in the year we've had him, he's NEVER pooped inside. He gets two, sometimes three, walks a day, morning, noon, and evening...should I try taking a treat with me and giving it to him and giving lots of praise when he poops? Anyone else dealing with a similar problem? Dachshunds are known for their stubborness...it's like living with a two year old perpetually! And please, before you all crucify me for letting him get infected, I was given wrong advice...I now realize even indoor dogs must be given prevention!