navbar not by title

I don’t want to display navbar with title of page for each item.
I want to show it with custom field that i will enter for each page.
So..custom field name will be navbar,value will be somevalue.
Now i need to change wp_list_pages() function.
Instead parameter title_li=& may be it should to be like a wp_list_pages(‘title_li=&meta_key=navbar’)…
In result it will display a custom field of some page instead his title.

thank you!