checking the form fields

Hi,

I tried to modify the poll script a bit. The qulity of the code is exceptionally high for this kind of tool.

If the user sends a comment, the input is checked before it is saved into the database. Where exactly is this check taking place? I`d like to

1. set a global flag if one of the fields "name", "email" or "comment" is left empty

and

2. I`d like to add a little email-validation script. I know that there`s a validation in the add_comment function. But this one takes place just before the input is written into the database. I want the validation when the form is processed so that I can give the user a feedback.

Where could this be done?

thank you - all the best,

Sacha