That's it !!! Big thank you w t ... it was due to that blank line between
table and the line "#+TBLFM"
Thank you Nick Docos too for your reply :)

cheers

Matt

On Sat, May 8, 2010 at 5:48 AM, w t <1218121@gmail.com> wrote:

> On Fri, May 7, 2010 at 7:21 PM, Matt Chastagnier <workandroll@gmail.com>
> wrote:
> > Hi,
> >
> > I've just started with org-mode and have done several tutorials. But I'm
> > stuck with this problem for 3 hours :
> >
> >
> > I have :
> >
> > | item    | quantity |
> > |---------+----------|
> > | laptop  |        4 |
> > | desktop |        7 |
> > |---------+----------|
> > | Total   |       11 |
> >
> > #+TBLFM: @4$2=vsum(@I..@II)
> >
> > I insert a new line [because I will want to add a new item] (M-S down)
> and
> > update the table (C-u C-c C-c) :
> >
> > | item    | quantity |
> > |---------+----------|
> > | laptop  |        4 |
> > | desktop |        7 |
> > |         |       11 |
> > |---------+----------|
> > | Total   |       11 |
> >
> > #+TBLFM: @4$2=vsum(@I..@II)
> >
> > but my formula isn't updated automatically so the wrong field is updated.
> I
> > would like the formula to become @5$2 instead of @4$2 automatically.
>
> Before editing the table make sure there is no blank line between the
> table and the line "#+TBLFM: @4$2=vsum(@I..@II)". Then use the
> M-S-<down> command.
>