How to build class library with cetain file extension

Question

Dear all,

I don't know if I post this question in the right forum category or not.
Apologize if it was.

Any way, I'm currently working with class library project (in VB6 known as ActiveX Library) to build class library (called as Add-in or plug-in) for the existing application program (.exe). This client application (.exe) requires my plug-in extension to be not  as the standard dynamic link library extension (.dll). But it require my plug-in extension to be .exp so that it could read my plugin in the right way.

My question: How could I change the default .dll file extension in to the .exp (or other type) file type extension?
I'm using VB.net 2008