1.6 How to restrict access to a shop with an access code ? [Multiple Shops]

[USB83]

Hi,

I'm using the multi shop feature that lets me have two online shops.

The default one for the general public : www.onlinestore.com

And a second shop : www.onlinestore.com/special that is offered to certain group of customers with whom i have an agreement to offer some discounts and some products that aren't available on the default "general public" shop.

I would like to know if there is a setting that lets me ask for an access code if someone visits the url of the second shop www.onlinestore.com/special
So the first shop is public, everyone can have access, but in order to visit the special shop, a passcode is required.

Is this possible with prestashop 1.6 ?

Thank you