Create API for .exe project (C++/CLI)

Hi,
I am really "stuck"  in my project and I really hope someone can enlighten me.

This is my problem.

I am tasked to develop an C++/CLI project which has 2 parts :

Part 1:  A EXE project which has a TreeView  

Part 2 : A DLL file  which has several API to the EXE project (Part 1) and these API must be able to give me information about the TreeNode of the TreeView  and also able to modify the TreeNode of the treeview.

Example : when I use GetParentNode() from the DLL, it is able to give me the information of the Parent node . Then,  When I use SetNodeValue( X1,y1,z1) , it must be  able to set the node value


Thank you in advance