Joao,

The variable cFiltro is going out of scope when the Init ends.

In the form designer choose New Property from the Form Menu item and type in the name cFiltro. In your form's Init put this code;

Thisform.cFiltro = documentosvenda.c_docum
set filter to documentosvendaseies.c_docum = Thisform.cFiltro

Also, check out my response to your other thread as it may allow you to can this whole filter idea. Fitlers on tables that are in a grid are very slow and there is little you can do to speed them up. The alternatives I presented in the other thread will be more flexible and faster for you.