Chirs has you on the path - with that EXIF reader, you want to find Unknown 93. The values within that contain your shot actuations since the last time Canon has serviced it. However, it is encrypted a bit:
From one of my bodies:
Unknown (0093)3,9 : 18,2,60490,0,0,0,65535,65535,1
Using the numbers after the colon as such
... : #, X, Y, #, #, #, Z, #, #
Whereby Z is always 65535 - the maximum number available to the counter
Y = the current counter number
X = the number of times the counter has rolled.
So, your current actuations is equal to X * Z + Y
In my case 2 * 65535 + 60490 = 191560
which means, I'll be sending it in very shortly to get the shutter replaced as I already have on my first body.
