Adobe Acrobat Javascript Calculation Factoring Checkboxes & Hidden Values

I need a little bit of help to put the final touches on my form. I need the Total box to add/display the correct value of the fields directly above it. It also needs to ignore the values of the two Checkboxes if they are not selected (the first Checkbox is read only). The Donation box part of the calculation seems to work fine, it's just that the total always includes the values from the 2 Checkbox fields even though they are not selected. I am donating my time to create this form for my local riding club, and only have a very minimal budget to work with.