Gr8 thanks Dude,
U done a good solution. but one item is missing . i also want particular IP or IP block to deny that site.
So as per ur suggestion and at last i found the solution.
acl office_time time MTWHF 10:00-18:00
acl bad url_regex "/etc/squid/block.acl"
acl lan_ip src "/etc/squid/lan_ip.acl"
http_access deny lan_ip bad office_time
But at last i thank u again