Sending some request to parent proxy

["Enrique" <enrique@xxxxxxxxx>]

Hi all
I have 2 squid proxy:  ProxyA and ProxyB,  ProxyA have more bandwidth so 
I want to configure the most fast as parent of the other but only some 
users request have access to parent proxy, the others users request will 
be send to default route.
I need some examples to do that please
sorry I don't know if I have expressed correctly.
sorry about my English
thanks