Help creating a Custom Action to determine Silent mode?

[mkarlesky]

I'm a Installshield beginner. Using Installshield 11 I need to sense
when a Basic MSI package is running in Silent Mode. Thus far, the best
thing I can find is checking if the UILevel is 2. I was successfully
accomplishing this in Installscript, but now I need to drop
Installscript support and use only a Custom Action. My attempts thus
far at using MSIGetProperty in a CA haven't been successful. Can
anyone provide some pointers? What are the basic steps? How can I
effectively test/debug my efforts? Are there any platform specific
issues (Win95/98?) I need to worry about?

Thanks in advance.

Mike