Possibly a scale count?
Has anyone heard of using a "scale count" method of sexing corns?
I read at a site called reptilerooms.com (?) that you can count the scales on the tail from the cloaca to the tip of the tail. You'll have to have kept a shed skin for this as counting them on a live snake will likely prove impossible. Males have longer tails than females (thus more scales). Count the two rows of scales on the underside of the snake from the cloaca to the tip of his/her tail, if the total of the two rows is 130 or less then it's likely a female and if there are 140 or more its said to be a male. Unfortunately a count between 130 and 140 could be 'either' so your mileage may vary...
I have no idea how accurate, or if this technique is accurate at all, but you can have fun with your magnifying glass and shed skin, then reply later and tell us your findings. Good luck!
Personally, I would like folks who already know the gender of their snakes to perform the count so we can find out whether or not this is based in fact or just a load snake poo.
Cheers,
Jason