Dog who only wants to potty in an area we dont want him to

Question
Patch, our 4-year-old Australian Shepherd, is the topic of this question. Patch has always been particular about his bathroom surroundings. Picky Patch is his nickname. He has to have "just the right" area, and he will often circle around and sniff out many spots before deciding on one.

For the first few years that he has lived with us our dogs went to the bathroom in the back yard. We have been doing some landscaping and now do not want the dogs tearing up the yard. Besides Patch, we also have a Beagle who likes to dig.

We currently have an area that is fenced off that has rock in it. This is where the dogs are supposed to be let out to go potty. The Beagle has no problems with this; however, Patch just doesn't like it. He hates walking on the rocks. I have put some plastic lattice pieces down, which he does like a little better.

He has never wanted to go to the bathroom on the rocks though. Up until now I have been letting Patch go outside in the actual grass rather than the rock area. I gave in to his stubborn manner, which now I am regretting.

I'm quite tired of picking up dog poop from the entire back yard and also the rock area though. Plus, when it rains it is just a hassle because we have to go outside to actually let him through the gate into the grassy area.

So, tough love has begun. Patch is going to have to learn to potty on the rocks. So far we're on day 2, and he still won't go. The boy will apparently hold it until the breaking point. I don't believe he has peed or pooped in those 2 days. Definitely not the latter and most probably not the former.

Any tips for getting this stubborn 4-year-old dog to give in and just potty where he's asked to go?

Answer
Unfortunately, Aussies are brilliant, and often they are "one trial learners".  He learned to prefer one substrate (I bet he learned it fast, too)!  Maybe you could think about putting grass in an acceptable area that you do want him to go in.
Or, think about going out with him to HIS preferred area for a while, and attach a cue to his actions.  Once you say "go potty" enough times as he is doing it, he may associate the words with the action.  Then, start going out with him to YOUR preferred spot for him to "go" and issue the cue "go potty".  Perhaps it won't take long for him to "get" that you want him to use a new spot.
As to the digging, most dogs never give it up - so, if you can't beat 'em, join 'em.  Create a "digging pit" and bury some milk bones in it.  Help the dogs to dig them up - yay, party time!!!!  Then, any time they dig elsewhere, redirect them to their pit, and make sure you occasionally have some "treasure" there for them to dig up (intermittent reinforcement keeps them going to that spot).  Good luck!