Question: Fields not recognized; how can I fix this?

I've got the following code to total cash on hand;

if (Sum(Hundreds, Fifties, Twenties, Tens, Fives, Twos, Ones, TwoDollars, OneDollars, HalfDollars, Quarters, Nickels, Dimes, Pennies)== 0) then $.rawValue=0

  else $.rawvalue = Sum(Hundreds, Fifties, Twenties, Tens, Fives, Twos, Ones, TwoDollars, OneDollars, HalfDollars, Quarters, Nickels, Dimes, Pennies)

  endif

I have verified that the fields I'm trying to sum all exist and that the spelling matches the actual field names. however, when I try to preview the form, I get an error indicating

"Error accessor 'Hundreds' is unknown."

If I take out the 'Hundreds' field, I get the same error for 'Fifties' and on down the line.

What should I be looking for?

Thanks much,

Katy