Im not putting up a tree this year for exactly that reason, my Jenson is nearly 12 weeks and I reckon it'sll be a nightmare.
I have got a spray you could try called 'keep off' I spray it around my pc and he hates it so never goes near it, apparently it's got lemon juice in which they don't like.
I paid a fiver for it from my local pet shop and you'll need to keep re-spraying every couple of days but it's well worth it and i've only got through half a can in a month xx