How can I use a third-party plug-in for MS Office in my program?

Question

API

There is a third party program that installs add-ons in MS Office. There is no official API for this program. It would be interesting to call this plugin from my program, as a kind of API. Is it possible to do this?
It is also interesting to know how plug-ins for MS Office are developed (what to read?).

Answer 1

msdn.microsoft.com/en-us/library/ms268878.aspx