OK I have 2 4-year old female Bichons and our house has a deck that is not ground level and it connects by a slider door to the kitchen. My mom and dad and I, although I have never been fond of it, have been letting them on the deck to do their duties. Also, they know how to do it on papers. Recently however I have been taking them outside to do their duties, and they do it. I walk to the door, have them sit and then we go out and then I give them a treat right there and then if they do it. Then on the way back, I have them sit again before going inside. Now when they have to go to the bathroom they still bark at the slider door to the deck. This is because they are used to that and sometimes my parents still let them out their, I think that's really odd. When will they start to bark at the front door? And what am I doing wrong, besides what my parents are doing. They don't even make as much as an effort as I do with bringing them out. I am starting to get frustrated

Keep at it. At 4 years old, the dogs are mature and slow to give up their long established routine. Dogs are very much creatures of habit. Parents too. I think you have done well retraining the dogs to go outside. You might try praising them and taking them out when they get near the door you want them to use. I have had to do that housebreaking a few puppies and suggest it in cases where the dog doesn't seem to catch on to going to the door.