Javascript function - Calculating total Form - Onclick gives value / add to total

I have found a 'calculating total' script which works well but I have tried to alter the script to better suit the needs of the site.

As opposed to having to type in each value I have also included checkboxes with a preset value. When you click on the checkbox it adds the total of ALL the boxes, NOT just the one which was clicked.

I have tried to include a javascript onClick= function but when I do, not only does the function not work, but the original script doesn't work anymore either.

I have included a link to my online "testing page"

http://www.romancandletours.com/contact/idex3.php

The upper part for "Group Tours" works perfectly, it is the lower "Private Tours" section which does not work correctly... when you check a box or make any change to the table the total jumps right up to 510. If you type a number into the "Number of additional People" it adds the amount onto 510 (40+510 = 550). I need the 2 sections to be calculated but why are the 3 checkboxes of 170 constantly being added up?!? The number 510 should only appear if all 3 boxes are checked.

Any help would be greatly appreciated!

Thank you

Ps. the version (5.x-0.0) is most likely not correct... I had to click something