Squidguard and selective download

[HD_CAIROCOMM]

I configured squid + squidguard and everything runs smoothly.
In the configuration I stuck downloading certain extensions with this expression ". * \ /.* . (Zip | rar | exe | msi | bat | cmd | .pif | src | scr | cab | php ? Id =)"
Now my question is: how can "authorize downloading" of one or more of these extensions from a particular site?

Tips or suggestions?