It was suggested in the IS newsgroup to use /D= but using the iscc.exe that came with version 5.2.3 I get an "Unknown option:" error.
Then in the script, how do you use the value of the command line parameter?
You do, as MicSim says, need the preprocessor. It's included in the latest ISPack. Once it's installed, iscc supports /D.
You can then use the values defined like this (assuming you'd done /DVERSION_NAME=1.23):
AppVerName=MyApplication v{#VERSION_NAME}