How to display a listing of custum field

Hello,
I created a page in order to dispay a list of all the items of a category with shortcodes:
[LISTINGS cat=’59’ orderby=’rand’ order=’desc’ show=10] : OK !!
Now, I would like to do the same depending of the content of a custum field I created when I start : Example: The custum field is named: “country” and I would display on my page all the items of my listing for example where the Country is “France”.
I tried without succes: [LISTINGS country=’France’ orderby=’rand’ order=’desc’ show=10] but it doesn’t work.
How is the correct syntax I must use ??
Thanks for your help.
Michel from France