>[I don't code much in VB]
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>I have a DLL written in VB, displays nothing when it runs. I want to change it to display a form with information that is updated as the DLL proceeds, in some cases, the DLL might be running for some time, and I need to know if it hung waiting for external events, or whether is is still actively processing data.
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>I also need a way for the user to press a button to get it to stop activity and terminate gracefully.
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>When I do a show form, I get
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>Non-modal forms cannot be displayed in this host application from an ActiveX DLL, ActiveX Control, or Property Page...
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>I can do a show vbModal but then it just sits and wait till the form is closed.

You cannot show a form from DLL, however you can communcate with the client application through raising events from your DLL. You will need to define your events, raise them at appropriate moment from DLL and receive the events in the client application using WithEvents. You can actually define only one event and just pass your different events and their values as parameters.
That will work just like you have a user interface with your COM DLL.

Or you can use out-of-process COM with a form, like others say.