Sophos XGS chnage outgoing WAN Address

Hello,

We use several networks and several public IP addresses, which are stored as aliases on the WAN interface. How do I configure the NAT rule so that, for example, the public IP address xxx.xxx.xxx.xxx is used for network A and the address yyy.yyy.yyy.yyy.yyy is used for network B? We want to communicate with the Internet via different IP addresses. What would be the best solution for this?

Thank you!