Plugins, hWnd pass-ons etc.

I am currently making a program with a plugin interface, but I have some problems regarding the way the plugins will be able to respond to the master program.

The plugins consists of ActiveX DLL's that is created by the master program using the CreateObject method. This way, the plugins may only send data and requests to the main program by responding to requests from the master program! How can I make it, so that the plugin can request the master program for data retrieval if possible??

I would also like the plugins to have full control of a textbox called txtMain (the program is a text editor). How can I do that? Is there any way VB can "simulate" a RichText field if given the hWnd of the actual text-box???

If you know how to do this, or have other suggestions you are more than welcome to tell me about it!!!

Thanks in advance...