The first part of your trigger needs to calculate the number of ticks the current fav price is about 3.25. Therefore use

g_ticks(price1, price2)

Returns the difference between price1 and price2 in ticks. If price1 is less than price2, the result will be positive, otherwise - negative.

so use g_ticks(3.25, r-1_back_price) to establish the number of ticks 3.25

now use

(0.003+(g_ticks(3.25, r-1_back_price)*0.003))*total_funds

as bet amount formula.

All this information is in the help document.

Always use TEST mode first.

Favourites of $3.25 have a 50% chance hitting 22 losers in a row. Thats 6.6% of your bankroll