Hi, don't forget there is a default
deny ip any any
line at the end of each access-list.
So if you apply you access-list as incoming access-list on the interface the traffic comes to from the user, it will block all IP traffic except the traffic from that one user to the proxy.
So you need to add a line
access-list 101 permit ip any any
to allow all other thraffic (with any destination different from the proxy) to pass.
Regards,
Milan