URL REWRITE

Hi to all.
..
i have some shops where i have installled a mikrotik for Customers.
I use firewall for secure wifi net, webproxy to block some pages, etc…

I have a url where depending of the source shop, it show any promotions or anothers, but the url is always the same.
i need add a variable in url when my customer go to page..
I mean.
by example: my URL is:
https://www.mydomain.com/index
i want that mikrotik add this variable in url.. something as:
https://www.mydomain.com/index?shop=myshop

is this posible with mikrotik?
please, note that url use https protocols (443).

i have tried with webproxy (in transparent mode)..but only works with http protocols, that is, i placed a rule in webproxy:
DST HOST = www.domain.com
Path= /index
Action= Deny
Redirect= www.domain.com/index?shop=myshop
In my test, only Works with http traffic, but dont Works with https..

Can not work on https, because the link between the remote server and the pc are encrypted and you can not see or change anything inside.