Multicasting

Assuming that the MPLS VPN in question is a service provider based VPN, then the frist thing to do is ask your service provide if they support Multicast VPN (MVPN).

If they do not, then you would need to set up GRE tunnels between you CE routers in order to propogate the multicast traffic.

To assist responders, you should provide more informaiton about your VPN network - like how many CE routers there are, what IOS version they are running ,what is the CE-PE routing protocol in use, what is the nature of the multicast traffic that you are trying to forward - i.e. hub to spoke, etc, etc.

actually i want multicasting in service provider network only

see Cisco doc "Tunneling to Connect Non-IP Multicast Areas"