That sounds brilliant osospecial.
We are only 5 days into the vt but so far we have done a combination of bribing/treating/withholding screen time to get the sessions done.
Ds has tried to negotiate a £5 per week incentive to do the daily sessions
, needless to say, I declined that suggestion 
We discussed that it woud be a good idea to do the vt before he has time on his ps3/iPod which he thought was a good idea ... until the following day when he conveniently forgot!
Best incentives for ds are- promise of arranging tea dates, money, snacks (not necessarily bad ones but they are preferred by him!), extra reading time at bedtime and just telling him he has to do it with loads of hugs and cheering praise when he finishes!
I can see that we will have to add to and alter these as time goes on though.
Yesterday, he was mollified by me making dd do her reading homework whilst he did the vt!
Pop how long would your ds sit in front of the computer for without starting? i.e. is he more stubborn than you?