How to differ between checked and unckecked

[Mohsen Pahlevanzadeh]

Dear all,
 

My program have a set of checkbox,
When user check a checkbox, i should
call slot1() and when user uncheck
checkbox, i should call slot2(),But
i can't understand when user checks
and unchecked.

My questions is, How can i find out
user check and unchecked checkbox?
It's very important that i differ
between check and unckeck.

Yours,
Mohsen