Hi jeen.john ,
That can be done using site to site VPN tunnel
network x------router a---------------site to site-------routerb-
you can build a site to site vpn with access-list on sida a would look something like
networkx-----to any
which means all the traffic going coming from site a would traverse the vpn and then on router b you can create a loopback interface send all the traffic from network X to loopback interface and configure ip nat inside on the loopback interface.
this is done so that due to ip nat outside on egress interface of router b , nat translations are built.
hope that helps
Thanks
Shakti