custom display for WOToManyRelationship destinationDisplayKey

Hello all,
I've been searching this week end on how to customize the display of  
a WOToManyRelationship destinationDisplayKey.
Here's what I have:
-a framework with my objects classes
-an application with a WOToManyRelationship

I'd like to change the value of the display string, but I just can't  
find how to. Precisely I'd like to get the value from a .strings file  
using WOResourceManager.

My issue is that I cannot use a custom method in the framework as it  
appears WOResourceManager doesn't work, at least I couldn't make it  
work (I used WOApplication.application().resourceManager(), but I got  
null value, and I didn't take the time to see how it would work with  
a language parameter, but it's not the point here;)).
So I tried adding a method to my application component class, but it  
looks like WOToManyRelationship doesn't even call my method!
And I would have to pass the destination objet to this method to be  
able to extract the requested key(s) and create the display string...

Does anyone understand me (I'm not feeling that much understandable  
right now)?
Do you know how I could achieve this?

By the way, is there any way to customize the sort ordering of a  
WOToMany?

Thanks for your help

Xavier