hi
the only way for you would be to have a trigger to record the max bank amount.
then have your bet value (your stake amount)+((maxbank-balance)*(1+commission)/(back_price-1))
this will place your normal stake with any loss that happens as betfair updates your account.
it would be the same for lay betting, but maybe maxbank-balance/2, so that you are recovering half the loss and it will get less as you win.
this will not recover your total losses, but will keep maintaining the max bank (this grows as you win)
it is a less agressive recovery method
mcbee