Howto define formula for table regions

[Torsten Wagner <torsten.wagner@gmail.com>]

Hi,

I am just playing around with the table function of org-mode.
I tried to create a little table to track the financial status of a
project. I thought it would be nice to distinguish between entries which
really had billed the account already and entries which will bill the
account in the future. This would allow me to track and compare the
current amount of my project account and in addition makes sure I will
not overdraw my account by missing an outstanding transaction.

Thus, initially my idea was to create a table like this:

|-----+------+-----------------------+--------+------------+------|
| nr. | date | title                 | number |     amount |  sum |
|-----+------+-----------------------+--------+------------+------|
|   1 |      | inital fund           |      1 |       1000 | 1000 |
|   2 |      | 1. payment to crew    |      3 |       -150 | -450 |
|   3 |      | 1. order              |      1 |        -50 |  -50 |
|   4 |      |                       |        |            |      |
|-----+------+-----------------------+--------+------------+------|
|     |      | balance on account    |        |            |  500 |
|-----+------+-----------------------+--------+------------+------|
|   1 |      | outstanding order     |      1 |       -100 | -100 |
|   2 |      | 2. payment to crew    |      3 |       -100 | -300 |
|-----+------+-----------------------+--------+------------+------|
|     |      | balance - outstanding |        |            |  100 |
|-----+------+-----------------------+--------+------------+------|

Now I would like to add formulas for:
1. Increasing the number of the first column ("Nr."), (entry in the FAQ,
I know), whenever I add a new row. However do this for two blocks and
leave row 6 and the last row empty.
2. Place the multiplication of "number" with "amount" in the sum column
3. Add the total sums of the two blocks in row 6 and the last row
(taking into account that the table will grow over time)

I know about column formulas and field formulas but I did not find a way
to do something like "for each field in column X between row a and row b
calculate ..."

I thought I could use the hline notation to encapsulate a undefined
amount of rows in between, however this doesn't work since every formula
does only refer to one field or to an entire column.

What I am looking for is something like:

$6@II+1..$6@III-1 = $4@0 * $5@0

or in text:

for each field in column 6 starting with the first row below the second
hline and end with row above the third hline multiply the column 4 and
column 5 of the current row.

Is there any other way to achieve this?
Or does this make much enough sense to implement it ;)
I guess there might be a lisp-way but I think a more intuitive way for
non-lisper might be useful.

As a kind of extra....for the very org-mode pros on this list
If I fill dates into the date column, a mechanism which moves
automatically (in the same way as I refresh calculation of formulas),
the rows from the second block into the first block when the date passed
would be some nice gadget


Best regards

Torsten

CC. The manual says, the very first hline will not be counted for the
hline referencing notation. However, as far as I can see it does count
in both formulas and by indicating it with C-} (Org-mode version
6.36trans (release_6.36.437.g05b7e))