Squid config - same user multiple ips

Try something like:

acl user41 proxy_auth manfred
acl user41 myip x.213.223.188

acl user42 proxy_auth manfred
acl user42 myip x.213.223.189

and leave the tcp_outgoing_adress as is.

EDIT: ah yes, maybe instead something like

acl ip_1 myip x.213.223.188
tcp_outgoing_address x.213.223.188 ip_1

acl ip_2 myip x.213.223.189
tcp_outgoing_address x.213.223.189 ip_2

and leave the proxy_auth acls alone:

acl user_manfred proxy_auth manfred

Then

http_access allow user_manfred ip_1
http_access allow user_manfred ip_2