It will be difficult to get a dog that was potty trained to go outside-to use something like that. I would guess that,even though it is on the balcony-and he has never been taught to potty there, he probably considers it part of the house. If you have a dog walker, and they come in the middle of the day, he should be fine to hold it until you get home. I have never used anything like that(for a dog....) but maybe someone else @pfgray2008
has an idea for you. If he is so well trained to potty outside-it would be confusing for him.