3 WAN ECMP and force several IP's to specific WAN

RouterOS Beginner Basics
1

Hi!!!

I tried to configure a RB3011UiAS-RM using this guide https://wiki.mikrotik.com/wiki/ECMP_load_balancing_with_masquerade in order to get 3 WAN load balance.

It’s works for almost all network clients but some of them must routed through just one WAN.

This is the current script:

/ip address
add address=192.168.1.2/24 interface=ether1 network=192.168.1.0
add address=192.168.6.2/24 interface=ether6 network=192.168.6.0
add address=192.168.7.2/24 interface=ether7 network=192.168.7.0
add address=172.16.0.1/16 interface=ether2 network=172.16.0.0

/ip dns
set allow-remote-requests=yes cache-size=5000KiB max-udp-packet-size=2048 servers=80.58.61.250,8.8.8.8

/ip pool
add name=dhcp ranges=172.16.0.40-172.16.9.254
add name=dhcp_pool1 ranges=172.16.0.2-172.16.9.254

/ip dhcp-server
add address-pool=dhcp disabled=no interface=ether2 lease-time=1d name=dhcp1

/ip dhcp-server network
add address=172.16.0.0/16 dns-server=8.8.8.8 gateway=172.16.0.1 netmask=16

/ ip route
add dst-address=0.0.0.0/0 gateway=192.168.1.1,192.168.6.1,192.168.7.1 check-gateway=ping

/ ip firewall nat
add chain=srcnat out-interface=ether1 action=masquerade
add chain=srcnat out-interface=ether6 action=masquerade
add chain=srcnat out-interface=ether7 action=masquerade

/ ip firewall mangle
add chain=input in-interface=ether1 action=mark-connection new-connection-mark=wan1_conn
add chain=input in-interface=ether6 action=mark-connection new-connection-mark=wan2_conn
add chain=input in-interface=ether7 action=mark-connection new-connection-mark=wan3_conn
add chain=output connection-mark=wan1_conn action=mark-routing new-routing-mark=to_wan1
add chain=output connection-mark=wan2_conn action=mark-routing new-routing-mark=to_wan2
add chain=output connection-mark=wan3_conn action=mark-routing new-routing-mark=to_wan3

/ ip route
add dst-address=0.0.0.0/0 gateway=192.168.1.1 routing-mark=to_wan1
add dst-address=0.0.0.0/0 gateway=192.168.6.1 routing-mark=to_wan2
add dst-address=0.0.0.0/0 gateway=192.168.7.1 routing-mark=to_wan3

How can I configure a address-list in order to exit by wan3 (192.168.7.1/ether7) for instance???

2 
/ip firewall mangle
add chain=prerouting connection-mark=no-mark src-address-list=<use_wan3_list> action=mark-connection new-connection-mark=wan3_conn passthrough=yes
add chain=prerouting connection-mark=wan3_conn action=mark-routing new-routing-mark=to_wan3
...