Docking a form in a dll into the exe main form

I have written in Delphi5 a small app with a main form, which
dinamically loads a dll having in turn another form. I would like the
dll form to be docked into the main form, so I set the main form's
Docksite property to true, and DragKind and DragMode to dkDock and
dmAutomatic respectively in the dll form.
However, this does not work. It seems that the main form does not
receive events such as OnDragOver,OnDockOver,etc.  concerning the dll
I have deduced from other posts that I should write my own event
handler in the dll form to send to the main form  the events that I
want the main form to be aware of.Is it true? Somebody could help me?
I am also thinking of implementing my dll form as a COM object. Would
this help to solve the problem more easily?