Chrome, one way to work out your commission is as follows -

a) download your 'Betting History' for required period - this shows net profit/loss figures for each bet prior to deductions for commission

b) download your 'Betting Profit & Loss' - this shows net profit/loss per race after deductions for commission

a minus b gives total commission paid for period.

I have found I can download the files & open them in excel 2007 but for example to use the data, I had to multiply the profit figures by 1 to be able to sum them, dunno what that's about.