Important - Please help

[hitec80]

Hi,
How do I do the following?

Lay £2 at lay price of 2.16

If the lay price decreases to 2.14 then lay £4 at the lay price of 2.14.

If the lay price further decreases to 2.12 then lay £8 at the lay price of 2.12.

If the lay price further decreases to 2.10 then lay £16 at the lay price of 2.10.

So basically you are doubling your stake each time the lay price decreases by a tick.

How do I do the above?

Please help

Thanks