Unless the betting pages are standardized it's not worth developing a bot that uses this. Some sort of formula needs to be developed.
When you say standardised, do you mean that they all need to have the relevant betting info displayed in the same format? If that's the case, they do already - here are a couple more examples: http://www.neopets.com/~innocent and http://www.neopets.com/~Assorted use the table format; it seems most betters format their information like this, if not all of them.
The table format is a constant for all of these pages, and all other information is unnecessary, except for the date of the bet. The way the Greasemonkey script currently handles incorrect dates (e.g. it is 25th April, and you attempt to use a betting page that gives you the bet information for 24th April) is that if it doesn't find the matching information (in this case, the odds ratios for each contestant) on the Neopets Food Club page, it doesn't make any bets at all.
Here is the GM script for reference:
I have no clue about programming and the language used for GM scripting might well be completely different from what you're using, but I hope this script was helpful in demonstrating how one programmer addressed the issue.