How to ignore horizontal lines in tables and references

[Benjamin Andresen <benny@in-ulm.de>]

Hello everyone,

I'm having a bit of a problem with tables and references. I try to use
tables + spreadsheet capabilities for data entry while testing certain
things, and one table design that works conceptually for me is the
following:

| Attempt | Start                  | End                    | Success | Wait in Min |
|---------+------------------------+------------------------+---------+-------------|
|       1 | <2009-07-31 Fri 04:43> | <2009-07-31 Fri 04:44> | No      |           1 |
|       2 | <2009-07-31 Fri 04:45> | <2009-07-31 Fri 04:46> | No      |           1 |
|       3 | <2009-07-31 Fri 04:48> | <2009-07-31 Fri 04:49> | No      |           1 |
|---------+------------------------+------------------------+---------+-------------|
| Results |                        |                        | 0%      |           1 |
#+TBLFM: $5='(ba/org-time-diff-min $2 $3)::@5$4='(ba/find "Yes"|'(@2$4..@4$4))::@5$5=vmean(@2$5..@4$5);%.1f

The problem I'm having is when my cursor is at @4$1 and I'm pressing RET.
It creates a new row where I can enter new data, as expected.

It will increment the
   @5$5 part to @6$5

Now the problem is when I try to automate the formulas a bit.

If I would instead of
  @5$5=vmean(@2$5..@4$5);%.1f
use
  @5$5=vmean(@2$5..@-1$5);%.1f
the following message will come up during evaluation:
  Row descriptor -1 used in line <line> crosses hline

Does anyone have any idea how I can make this work? The problem goes
away when I delete the horizontal line. If my table design is wrong or
there is a better way to do what I'm open to changing it.

Thanks in advance,
benny