[AccessD] Using the recordset of a list control

Hi all,

I have a form with a list control.
The list displays quantities and amount.
Under the list, I have some text box that should display the total of these
quantities and amount.

What I do is to use the recordset of the list, to scan each of the record
and do the sum I need.

The problem is that this recordset does'nt seem to be reliable.
Sometimes it does'nt exist anymore, sometimes it has 250 rows instead of
just 5 to 10.
The calcultaion is ok only the first time i do it, and then it's not!

Did you already get into these kinds of troubles?
What am I doing wroung?

TIA,
Philippe