ActiveX DLL failed to run in OL form

I have written an ActiveX DLL using VB6, compiled and located at my computer, but this DLL failed to run in my OL form. However, no problem arise if i put the DLL under MTS (which is located at my computer too). The error i got from OL form is something like ” … the DLL didn’t register correctly, please run the program setup again …”. This DLL is running fine inside a VB EXE project, but i dunno why it can’t run in OL form. The code which i used to create the DLL from OL as below.

Dim myObj
Set myObj = Item.Application.CreateObject(“myDLL.myClassName”)