How to set the lay stake > back stake ?

[alexyo]

My betangel is setup to lay 3euro and back 3 euro.
For example if I lay at odds 2 with stake 3euro the angelbet back at odds 2.1 with stake 3euro.
In this case I have profit only in back market.
I want the back stake to be lower than lay stake to have profit in both cases.
I use 'fill or kill with offset'.
How to do that?