[Orgmode] table formula question

[Eddward DeVilla]

Hi,

   I'm having trouble trying to figure out what I've got wrong here.
Given the table

* wealth management
 |--------------------------+--------+-------|
 | item                     | amount | total |
 |--------------------------+--------+-------|
 | paid                     |  50.00 |       |
 | baby's new part of shoes | -25.00 |       |
 | chip                     |  -2.50 |       |
 |--------------------------+--------+-------|
#+TBLFM: $3='(+ @-1 $-1)


I would expect to get the results

* wealth management
 |--------------------------+--------+-------|
 | item                     | amount | total |
 |--------------------------+--------+-------|
 | paid                     |  50.00 | 50.00 |
 | baby's new part of shoes | -25.00 | 25.00 |
 | chip                     |  -2.50 | 22.50 |
 |--------------------------+--------+-------|
#+TBLFM: $3='(+ @-1 $-1)


But instead I just get

* wealth management
 |--------------------------+--------+--------|
 | item                     | amount | total  |
 |--------------------------+--------+--------|
 | paid                     |  50.00 | #ERROR |
 | baby's new part of shoes | -25.00 | #ERROR |
 | chip                     |  -2.50 | #ERROR |
 |--------------------------+--------+--------|
#+TBLFM: $3='(+ @-1 $-1)


I'm sure I'm missing something.  Is a table like this even possible?

Edd