that's what i'm missing....damnit. Is there any 100% accurate way to calculate it? Can't the program itself do it somehow?
Just generate the list of PIDRNG frames for your seed, and compare the nature, ability and sex of the pokemon you've caught with those listed.
To be more accurate, you can use the %6 method.
%6 is for finding the characteristic a PID will generate for a pokemon with 2 or more IV stats tying for the highest. Using this you can eliminate many PIDs from the list when trying to find where you are on the list of frames you have generated from the seed in the main Reporter window.
Use Windows calculator. Under View, choose Programmer.
Set it to hexadecimal.
Paste in a full seed.
Set it to decimal and seed is converted. Copy the converted seed.
Next, under View, choose Scientific.
Paste in the converted seed, key in Mod, 6.
The calculator will display the remainder.
Loop clockwise: HP(0) - Attack(1) - Defence(2) - Speed(3) - Sp.Attack(4) - Sp.Defence(5) to make a hexagon.
Mark which IVs are perfect on the pokemon you've caught. (Ask the judge.)
The number of the remainder is the number of the stat which the characteristic will refer to, unless that stat is not perfect. In that case, travel clockwise around the loop to the first perfect stat you come across, and that one will determine the characteristic.
If the PID gives a characteristic other than that your pokemon has, it cannot be for the frame you've hit.
There's also a way to get Reporter to do this, but I haven't got my head around that yet, so I'm still using the old way.
Jolteon might explain the more up to date method if you're interested.
However, before you bother with the above, give Jolteon's formula a try, and see how you go with it. If it doesn't work straight off, at least you'll know the area in the list to start looking in.