Hi Anneli! If I catch them in the act, I just keep everything about my voice and body language very neutral. If they start to realize that they can get a reaction out of you (positive or negative attention is still attention and therefore a reward) by going potty in the house, that will open up a whole new can of worms. So usually, I'll calmly but firmly touch their side to make them stop and then move them outside. I don't say anything while doing this, but if they finish going outside I praise afterward. Does that help?