Hello,
I specialise in COM development using C++ and acn help you. 20 years experience should help.
Having said that, I haven't heard of ImageMagik before- so .. can I take a look at the files that comes with this software- alongside the DLL you have referenced in the job ?
Depending on the version of Windows this software is designed to run on(i.e. targetted at), you may need to include COM related support files such as registry files(.reg) and - for development purposes- .TLB (type library), which is needed, in order to access a COM object from VBScript(if my memory serves me correctly).
Anyway, let me know