Determining who is calling a COM objects/automation server?

Hello,

We have an Automation server which exposes
various COM objects. However, for security
reasons, we'd like to determine who (which
program and/or DLL) is invoking the various
methods of the COM object from within the
implementation code of the COM object.

Ideally, we'd like the users to be able specify
which applications and/or DLLs can invoke
methods of the object, and be able to alter
the behaviour of the method based on this.

Does anyone know if this is possible?

Thanks,

Brett