Unusual Auto Updating Percentages in Input Boxes?

[socalnate]

Here's an unusual AJAX script I need some help / suggestions on. 

 

Go here:http://dev.egamestorm.com/submit.php

 

Notice the "Select a Genre" section with percentages:

 

I need the Select A Genre section to...

 

1) Give me a warning message if I haven't entered any percentage value into any of the input boxes

2) If in any of the boxes the value x>100%, highlight that box in red with a warning message "Can't be greater than 100%"

3) If in any of the boxes a negative value is entered a warning message appears "Can't enter negative percentages!"

4) If the TOTAL VALUE of every box is greater than 100% give a warning message "Error: Total Percentage is over 100%!"

 

How the heck do I do this?  ???