checkboxes in livecycle designer ES

I am trying to add a calculation to a PDF registration form we use at work.  

There is a section of the form where the registrant is supposed to check a box if they are attending single days of a conference (mon, tues or weds) with each day being $650.  We have this same function for exhibitors - they need to select which day they want to attend.  There is also the option of full conference attendance and spouses, and just to make things interesting, early bird and regular parameters also.

I am running into problems trying convert the checkboxes into a calculation that will create a subtotal.  I have posted the form here if you want to see it:
http://www.healthcaredistribution.org/test/regform-v4.pdf

I think I am supposed to use the binding property of the checkbox object - the on value is the cost of the particular registration type and the off value is 0.

Here is the scripting I have setup to start testing:

 form1.Page2.subtotal::calculate - (FormCalc, client)
--------
SUM(form1.Page1.memberfullearlybird_1050.bind+
form1.Page1.memberfullregular_1300.bind+
form1.Page1.memberdailyearlybird_650.bind+
form1.Page1.memberdailyregular_650.bind+
form1.Page1.exhibitordailyregular_350.bind)

Once I figure out what actually works, I will add in the rest of the necessary checkbox values.

What am I doing wrong?  Should I be using JavaScript as opposed to FormCalc?  If so - what would something like this look like?

Thanks in advance!