navigation link based on custom field

I’m looking for a method to order posts by a custom field so that the navigational links on a single post template would point to the next or previous post in the sequence defined by a number in a custom field.
Note: The posts are all in the same category.
I can define the list of posts in the category in the order defined by the custom field value but when I view the single post, with a template modified to show only the selected category, the nav links at the bottom of the page are based on chronological sequence.
What I need is a way to link to the next/previous post in the same category, where the order is defined by the custom field value.

Is there anyway to override the chronological ordering of the posts?

Thanks.