Automating MS word on a web page

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C#

Javascript

interop

MS-Word

I'm converting an ASP Classic project to .Net, The original application uses something along the line of:

this.oWord=GetObject("","Word.Application");

to display an instance of Word in an iframe using an ActiveX object.
The web page contains controls to do fairly sophisticated control of the opened Document. The code for those looks like javascript, but I'm pretty sure it is JScript. Not only do web page controls save the document, they insert bookmarks.
Yes, I have a problem.
This is an internal Intranet application, not Internet, so it will only run on a PC with MS Word installed. I have a lot of control available.
Can anyone offer any suggestions? Any Approach? I'm wondering if it might be possible in a Windows Form Application, but that would be a very last resort and I'm not sure the client would accept that. (Whoever wrote the original ASP program was very good.)
Thanks much, Mike

What I have tried:

I have extensive knowledge using the MS Interop and the OpenXML SDK (Oh Joy). This project has had me unzipping .DOCX files and manually updating XML that had become corrupted. (Hey, I programmatically manipulate even PostScript files for this and read PDFs as text files for info in them.) Oh yes, I'm all for any cheap thrill.