about packet flow and mark packet

hi all this is my 1st post
i have 3 interface on mt box and the network like below:
internet ----- a MT b----- client
c±-- d squid

a. 192.168.10.1 == public
b. 292.168.1.1 == local
c. 192.168.5.1 == proxy
d. 192.168.5.2

here my nat:

/ip firewall nat
add chain=src-nat out-interface=public
add chain=dst-nat protocol=tcp dst-port=80 action=dst-nat to-address=192.168.5.2 to-port=3128

i want to capture the packet that request from my proxy to client and from internet to my proxy

i already try using forward but, it’s useless
if the client set their browser proxy to my proxy, he can’t be queue

pls hlp me

thanks