(Yes, I'm still standing lol)

Hi my friends of the new continent, (and all around the world !!!)
It's a long time I didn't come on this forum.
I have (as usual) a stupid question about customization with 68classifieds. I'm with 4.2.1
The situation : the real estate agencies I'm working with, put some ads. But I had to manually create in the database a column in 68_listings called 'localization', because the 'city' field -of the user- doesn't match with the places of the houses sold (no extra field, for the reasons below).
I'd like to display categories and subcats specifically for the region (and only display the ads of this region) :
I think the url would be something like that :
http://www.myads.com/category.php?localization=zone1 for the main categories, and
http://www.myads.com/category.php?ca...lization=zone1 for the subcats.
I'm sure it is possible to do that with v4.2.x, but I really don't know how (and where) to do that.
If you have an idea, you're welcome (please contact me by PM if you can make me an offer for this work). If you want some extra explanations, you're welcome !
Best regards from France
Pascal