Cant get him to use a tray

Question
We moved from a three bedroom house with a backyard to a small unit in the city with a balcony about 3 months ago with our little chiuaua/shi-tzu cross.  He's 8 years old, very good and has adjusted very well, not barking or anything.  At the old place we had a doggy door for him, and he could obviously go when he wanted, whereas now are taking him for walks 3 times a day.  He doesn't specially ask, he just holds on till we take him, but he's always happy when we do - when we get up, in the afternoon, and before we go to bed.  Obviously it's not always easy to manage 3 times a day, so we've put a tray on the balcony for him, filled with bark (thats what he liked to go on at our old place), but he won't go on it.  Would rather wait till we take him.  I posted a question on a forum, and they suggested teaching him to go on command when we take him to the park, and then telling him to go in the tray.  He is now happy to go on command to "Do Puddles" when we're out, just about anywhere - in the park, on the bark on a ledge, on the dirt, etc - everywhere we tell him - except in the tray on the balcony.  We've tried walking him, and taking him to the balcony, so it's like the same procedure, but he just stands there shaking.  We've also tried taking a container down to the park and catching his pee when he does it, and tipping that into the tray in front of him as we tell him etc.  We also tried one day not taking him for a walk in the morning, just put him straight onto the balcony, and shut the door.  He sat there whimpering for hours, and finally started barking.  My husband yelled at him to stop (if the other residents hear him and complain they can kick him out), and he peed right there in the doorway, then continued just standing in it, looking in, and fretting.  By mid afternoon we just felt so guilty that we let him in (washed his feet of course) and took him for a walk a bit later.  He acts like we're bullying him, and I feel really frustrated - we're doing this for him and he behaves like we're terrible.  We haven't smacked him in the tray, or done anything to make him feel like that.  I don't know whether he really has no idea what we want, or whether he knows exactly, but doesn't want to as he enjoys going for walks all the time.  I just don't know what to do.  He's not stupid, he's learned other things, I'm sure he should be able to learn to go in a tray.  The tray itself is wooden, lined with plastic and filled with bark (never been used by another animal or anything).  It's about 1 metre long, by about half a metre wide, and about 15cm high.  He doesn't have any problems jumping in and out of the tray, and is quite happy to jump in when we promise him a treat, but he won't do anything once he's there.  Just waits till we say he can get out, or we go away.  Or else shakes, as we're telling him to do "Puddles".
Please  - what can we do??  Any suggestions would be really appreciated.

Answer
Your dog has a fear of this tray now from trying to get him to use it.

all dogs adjust well and you may just have to keep him on a schedule of getting up an taking him downstairs to go potty several times per day.


they also make a dog litter box in pet stores with special litter you may want to look into.