[Orgmode] Question on spreadsheet formula

[RC]

Hi,
On applying the column formula on the table shown below:
  |-----+------+------+----------|
  | No. |    P |    E | B        |
  |-----+------+------+----------|
  |     |      |      | 0        |
  |   1 | 5000 | 2000 |          |
  |   2 | 7000 | 1000 |          |
  |   3 | 5000 | 1000 |          |
#+TBLFM: address@hidden

I get:
  |-----+------+------+-----------|
  | No. |    P |    E | B         |
  |-----+------+------+-----------|
  |     |      |      | B         |
  |   1 | 5000 | 2000 | B + 3000  |
  |   2 | 7000 | 1000 | B + 9000  |
  |   3 | 5000 | 1000 | B + 13000 |
#+TBLFM: address@hidden

When what I would like is:
  |-----+------+------+-------|
  | No. |    P |    E | B     |
  |-----+------+------+-------|
  |     |      |      | 0     |
  |   1 | 5000 | 1000 | 3000  |
  |   2 | 5000 | 1000 | 9000  |
  |   3 | 5000 | 1000 | 13000 |
#+TBLFM: address@hidden

Is there a way I can restrict application of the column formula to below the
horizontal line.
Thanks,
RC