As yankees or parlays as we know them must be placed on the same state meeting (ie they must all be on sydney meeting ) here is a method of calculating the amounts for each combination that works out pretty close to the same amount place individualy and you could also back in serveral states

say you have $100 to invest on your parley over 4 races, on the first race you put 60% of your bank, in this case thats $60 on the first selection if you get a return add it all to the remainder of the original $100 thats $40 plus return...i will give you example over a winning 4 race situation

bank $100
first bet $60 ramainder $40
place paying $1.50 return $90
total $90+$40=$130

Bank $130
second bet $78 remainder $52
place paying $2.00 return $156
total $156+52=$208

bank $208
third bet $125 remainder $83
place paying $1.50 return $187.50
total $187.50+$83=$270.50

bank $270.50
fourth bet $163 remainder $107.5
place paying $2.00 return $326
total $326+$107.50=433.50

Now this could continue with another bet if you want now if any of these lose you start your bank with the remainder of the last total.