[MatthewS]

Sounds like you're looking for an inspector or palette that lets you customize individual borders as if it was a characteristic of an object. I don't think OG has that.

Only way seems to be anchoring four separate lines objects together, so that you can control the line widths separately. (It could be one of those things you do one time and make it a stencil or master object so you can change it globally later.)

A feature like this appears in other apps such as InDesign and MSWord. Visio has it but it's wonky.