Retrieve all record if check box = 0 (Not checked)

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