Carlos,
Start with creating a query which would have your criteria for reaching
zero, like a Totals Query which would total the amount. So, if your query is
called qryFindAmount and the field in the query is called TotalAmount then,
in the code listed below for the "IF" statement put:
If DMax("TotalAmount","qryFindAmount")= 0 then
You will also need a field for the email address. In the code example
below, I called the field EmailAddress. This field needs to be on your form
or referenced in a query.
Then, on your form, either on the After Update event of a field (like your
quantity field), or on a button, click on the drop down and pick [Event
Procedure], then copy the code listed below with the correct query
information as shown above and paste in your Visual Basic window.
If you set up the format of your query and the field name for your Email
address, I can help with more specifics.
Jackie