I will take a wild hit and say that you probably want the office application to call home to your exe? In this context, exe is the server, and the office application is the client.
If you are using .NET 3.0, WCF is most likely your best bet. I would build a solution in three parts:
- " " . , . , , . . . "" " .
- "". "exe" , . ServiceClient . , ServiceClient ( -, tcp ..). . " " .
- "". " " - . svcutil.exe.
"exe" "plugin" , .
, " " -. , .
WCF .