Assign different local IP for each TCP Session using iptables

I have a service in a client that accept only one connection per IP address. Due this security directive, I followed the article https://access.redhat.com/knowledge/solutions/21614, but with no success.

I used an IP range like this:
iptables -t nat -A POSTROUTING -d 32.8.0.0/16 -j SNAT --to-source 10.8.81.49-10.8.81.62

If I did two or more connections from the same source (client) station, all the connections are mapped to the same SNAT address by iptables. I need to map each TCP session to a different address, to allow N connections from the same source station. Anyone know if is it possible to do using iptables?