How to save an unknown Interface to a Pointer?

Can I save an unknown interface to a pointer ?

For example I have an unknown interface and want to save it to a TreeNode Data?

var
  X : Inknown;

To save :

....  
  Node:=TreeView1.Items.Add;
  //Node.data:=x; //compiler won't allow this
  Node.data:=@x;
...  

To get :

...  
var
  //X:=Node.data; //compiler won't allow this too
  Pointer(X):=Node.data; //an exception caught
...