ICM on the fly

I am a great fan of ICM to make those crucial tournament decisions, but struggle to find a way of doing the maths on the fly - that is, in the heat of battle. Perhaps this is best illustrated with the example that lead to this post:

pokerstars $5.00+$0.50 USD Hold'em No Limit - Level VIII (200/400)
(PAYOUT 50% 30% 20%)
Table '225618752 1' 9-max Seat #6 is the button
Seat 1: SB(4470 in chips)
Seat 3: HERO (4547 in chips)
Seat 6: BTN (4483 in chips)
SB: posts the ante 25
HERO: posts the ante 25
BTN: posts the ante 25
SB: posts small blind 200
BB: posts big blind 400
*** HOLE CARDS ***
Dealt to HERO[As Qd]
BTN: raises 4058 to 4458 and is all-in
SB: calls 4245 and is all-in
HERO ?

I reckon I ballsed it up by folding, thinking I'd guaranteed 2nd place (worth $4.50 more) with a playable stack heads up. What I forgot was that as I was very very slightly chip leader, barring a tie between other two that beats me, I get 2nd even if I lose.

This is how I did the maths later:
I ignore the tie (correct?) and put myself at 40% to win. Whether I call or fold I get second place so the decision is about the difference between 1st and 2nd, i.e. $9. The call is worth 40% of $9 = $3.60; the fold is worth 4147/13500 (my stack as proportion of chips on the table) x $9 = $2.76. ( I think the maths is good here - feel free to say otherwise.)

So, in this type of situation does anyone have a way of drumming up these figures in the moment? Or, to put it another way, can you figure the correct play if the hero's stack was 100 smaller or 1000 higher, in 30 seconds?

I'm only interested in the maths here so please don't post "Hey man I'm shoving all day long here, I play to win!!"

Thanks

Abuuuuuuu!
Moley moley moley mole!

On a more serious note, you just opened up a whole different kind of math that I have to learn. Thanks.

you can get an icm calculator handy on another screen.. myself ive played a lot of sng and i can sort of work out when its a good spot to push, fold etc, just from experience, and from going back through HH and reviewing it with SNG wizard.. but im not sure of the math behind it, i for sure cannot work that out in the space of 30 seconds and generally im playing 8 tables at once so it becomes impossible...

I'm not sure there is a quick way short of a program, and I think using one is against the ToS in some places. I wrote one myself a while back for analyzing my play. Turned out to be really easy because it's basically a recursive calculation. I've thought of seeing if you can graph it and just keep the graphs handy for lookups, but haven't gotten that far yet.

RF