Who's been peeing in the computer room?

Right, it's been Dock.  With 2 cats, it's hard to figure out who is peeing where, especially when it is not in the litter box and you don't see them.  I have found a few spots lately, and they have been in various places including the computer room where Dock eats her meals.  Now, male cats tend to have a few more issues with this (and Mace would fit that bill) because  they tend to get stressed more due to lack of enrichment, exercise, attention, etc.  Dock being so relaxed, and Mace being Mr. Crazy Pants, let me believe it was Mace.  But if it has been in the computer room, then I suspected Dock.  And due to the early kidney disease, and the pred, I was pretty sure it was.  Well literally about 5 minutes ago, she was on the cushion my hubby had put on the floor.  (His back was a bit sore, and needed it for a bit of lower back support while on the computer).  It was the kind of cushion you have tied to your dining room chairs, and it has a few sewn circles to look like buttons. Well, Dock as pawing at them (never seen her do that).  I thought, why is she playing with those circles, do they feel odd on her paws?  then she lifted her tail ever so slightly.  I caught her before she started.  Whew.  So once she's done her breakfast, I'm sure she'll make a break for the litter.