Automatically select Check Box

I'm hoping someone might be able to offer a suggestion. I'm trying to create a script that would automatically insert a check into a check box if the sum total of another field in the form is greater than a specific number. In other words, if someone enters a number greater than 10 in field sum.total, then a check would automatically be inserted into a Yes checkbox. If less than 10, a check would automatically be inserted into a No checkbox.

Thanks in advance for any suggestions/thoughts.