Filter SubGrid with related data from N:N relationship

Hello,

I Have an entity called  "Project"  it's related to "Account"  with  N:1  relationship.

I have a N:N relationship between "Project" and "Contact"

So for every project  I can  add  many contacts .

Now I have a SubGrid  that  shows  a list of contacts  for the project and add existing one.

The problem is : when I use the Search look up  to look for  contacts , I get all contacts from the system

What I need Is : to get just  the contacts  from the  Account related to the project.

In other words : for every project  I want to add  many contacts from the account related to the project


Thank you !