Hi Debbie
When dogs get upset about being left alone, it seems it is the first few minutes that are the most critical. So if you can get him to be calm about you going, and even engaged in some other interesting activity for that time, you should be able to beat the barking thing.
Two things you could try. One is to desensitise him to you leaving by practising leaving. If you "leave" the house for just a few minutes (just go outside the door) and then return - making absolutely no fuss about going, and especially about returning (don't acknowledge the dog when you come back in, just go check your mail or some other normal activity - and greet him only a few minutes later after he's gone and sat down again) then your dog should come to view this as a non-event. Practise it often - just as a matter of routine and with no fuss attached. Sure, you'll look silly standing outside your house at regular intervals, but the idea is that your dog will become bored/desensitised to the event. So you need to be repetitive about it.
Another thing you can do is to leave your dog with something to do. A frozen kong, or a treat ball that he needs to think about how to tackle can be good options. Another one is a small brown paper package of treats that he's going to have to work out how to get into. If he's engrossed in that for the first half hour that you're gone, he is far less likely to bark in protest to you going.
Give those things a try - they're often fairly effective. Leaving him with a radio or TV going may also be helpful. Not really sure why that works, but in some cases it does - perhaps it just stops the house being unnaturally quiet.
You can also try a search of the forums using the term "barking". Plenty of people have had this probelm in the past, so reading some of the suggestions given in previous threads may bring up some more ideas. Good luck
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