Silvio if i am understanding you:
1. the form should have all records.
2. on a form you have an unbound check box where if you check it, only -1
records appear, otherwise all records are visible.

if that is correct:
on the after update of CheckLab

If CheckLab = -1 Then
Me.filter = "lab= - 1"
Me.FilterOn = True
Else: Me.FilterOn = False
End If

you might have to play around with the quotes in the filter and/or how to
handle the else
good luck anf i hope that helps

"Silvio" wrote:

Hello, I would like to see ALL (0 and -1) records if my check box in my form
is not checked (0) and if checked (-1) I would like to see only record with
-1 (with check mark)

This is what I have, but as expected it will return only record with 0 OR -1

SELECT tblSite.Site, tblSite.Lab
FROM tblSite
WHERE (((tblSite.Lab)=[Forms]![My Sites Groups]![CheckLab]));

Thank you,
Silvio