Scripting calculations for subtotal and taxes = grandtotal

I have a work form that lists cost of work preformed. 4 amount fields, a subtotal field, tax, and grand total. I am having an issue collaborating the subtotal, taxes and grandtotal. I have googled everywhere just for basic FormCalc help but to no avail. Any help you can give me will be very much appreciated.

this is the script I foolishly 'thought' would work.

Subtotal - Sum(AMOUNT, AMOUNT, AMOUNT, AMOUNT)

Tax - Sum(TOTAL * .0825)

Grandtotal - SUM(TOTAL, TAX)

I have ran the syntax check on all fields no errors, but I get some extremely weird output when integers are place in the amount fields.

layout --------------

amount

amount

amount

amount

subtotal

taxes

grand total

they are all numeric fields (i don't know if all this is relevant but I'm trying to make this as easy as possible for you to troubleshoot)

thanks in advance

skyler