price difference

Hi, I am quite new so I got basic question:

How to check price difference between favourite and second favourite? back and lay?

Hi
for tick difference use g_ticks(price1, price2)
r_ = rank

example:
price difference in ticks between favourite back price and second favourite back price
g_ticks(r_1_back_price, r_2_back_price)
condition would be:
selections trigger expression g_ticks(r_1_back_price, r_2_back_price) is greater than 20

or for price difference just subtract the prices
r_2_back_price - r_1_back_price

Very helpful, so simple - big thanks