Gambling winnings would be treated as a windfall and most IVA's allow you to keep windfalls under £500, so it should be OK ( but some IPs might think differently). However, creditors would not look kindly on you gambling and it would look like that is what you are doing --- it is your bank account and your responsibility --- and it would be difficult to prove otherwise. It might be an idea not to do this again.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014 http://foggy.blogs.iva.co.uk