ok lets say u have Extended ACL

access-list 100 permit ip 192.1681.0 255.255.255.0 any

then u need to match any traffic from that subnet going to any distination with TOS DSCP ef

do the following

hostname(config)#class-map match-all voice

hostname(config-cmap)#match access-list 100

hostname(config-cmap)#match dscp ef

then u can apply it to whatever interface or globaly (to all interfaces)

the following link contain good details regrading ur question

http://www.cisco.com/en/US/products/hw/vpndevc/ps2030/products_tech_note09186a008084de0c.shtml

good luck

please, if helpful rate