problem getting a value back from 3 project chain

Hi

i have a project which is creating an instance of a form thats on another project (dim newForm as New Prj2.Form1, something like that)

on that form ill hope to get some information from the user then it will call another class(same project prj2)

which will then call another class on another project through an interface (dim ext as new ....)


its all just for testing right now, no real functionality
whati want to achieve is when the project runs
press button on prj1.form1
it open the window contained in prj2
user enters a string and presses a button
code then instantiates a class still on prj2
this class is an MEF container class, which calls an imported extension through an interface that on prj3
the ext will just return the string + "Ext Executed" so i know the string was processed back to container class
the MEF container class will return the value back to prj2.form (here is the problem, this form doesnt really need this information, its the form on prj1 that needs it)

how do i achieve this?