condition to not place bets above x liability

Hi, I want to make a condition so that the trigger does not place any bets if the liability exceeds a certain amount. What is the variable I need to use?

Hi
formula for laying to a fixed liability is:
liability/(lay_price -1) = bet amount
e.g. for a liability of 100:
100/(4.2 -1) = 31.25

so you could make a condition:
and selections trigger expression bet amount*(lay_price -1)is equal or less than 100 
e.g. for bet amount of 50
50*(4.2 -1) = 160
the condition will return FALSE 


  

Thanks Mark,
I can use the 2nd solution you gave.
I wanted to set a limit for the amount the bets can get up to.