As markysharkey
says, if you've the right IOS version, this should be easy enough to do in rough pseudocode
ip nat inside source list [your NAT ACL] interface [wan interface to Rogers] overload
[your NAT ACL]
permit 192.168.100.100 255.255.255.224
permit 192.168.100.170 255.255.255.255
deny any any
My 00000010bits
Regards