Well you probably have an access-list specifing what to NAT, e.g. "access-list 102 permit ip 172.29.4.0 0.0.0.255 any". If you don't use an extend ACL, then please do, but put a deny statement in on the top, like so:
access-list 102 deny ip 172.29.4.0 0.0.0.255 192.168.0.0 0.0.0.255
access-list 102 permit ip 172.29.4.0 0.0.0.255 any