Logic Error On Limiting The Modification To The Maxvalue ?

How to create a function that would allow me to add to or subtract from a maxvalue, and thankfully I got help regarding that. However, something's got me stumped for the past few weeks that I still can't resolve...

This is the relevant code:

As it stands, it works as long as the total value is less than or equal to the limit (for advantages it's 15, for disadvantages it's 10). However, the moment it goes past the limit -- for instance, if you change Antisocial's value from 2 to 7, or if you add several additional checkboxes with any values -- the whole thing starts going crazy; specifically, maxvalue doesn't revert to 40 when the all the checkboxes are unchecked.

What I'd want to happen is that the user cannot select or apply advantages or disadvantages if the maximum advantage is greater than 15 or the maximum disadvantages is greater than 10.

I'm thinking that a button for adding disadvantage points to/subtracting advantage points from the maxvalue (that becomes disabled if the user goes past his limit on advantages/disadvantages) is useful at this point, but I'm really stumped on the implementation of the idea. An alternate idea of mine is that all other advantage/disadvantage checkboxes would become disabled if their value is greater than the remaining number of points, but I don't know how that is possible either.