MSI automation - Callback?

Hi folks,

i played around with the MSI automation interface and did some VBS on MSI files and on the stuff that is installed on the current workstation. It's pretty cool, what one can do with it.

However: I have a spezial task and still don't know how to solve it:

If I start a MSI using automation (vbs or C++ ...) or with the MSI APIs - how can I get a callback into my program on every install step or - at least - every time the progressbar advances?
My aim is to provide a own progress bar and to know how far the installation has advanced (to write .log file etc.)

Any idea?

Best regards
HoM