I hope Clare (Clarenmax) will see this soon... she has a plenty of experience to share...
Lol, indeed I do
It took me about 3 days of perseverence to get a sample from Max the first time around!
The vets gave us the special litter, but he refused to go anywhere near it most of the time.
I figured the best way was to put this down until he needed to go, then put back his normal tray and stick a shot glass under the stream to catch it! Not the most dignified way of doing it, but its now tried and tested in my house
Does Barney use an indoor tray as well? If so you could confine him to the house for a while to make it a bit easier?