ITNinja

I have developed an .msi with user giving certain values using the dialogs. My manager asked me they wanted the same app to rerun multiple times on the same machine. I sorted out using multiple instances..Here comes the issue, There is a user input which should be unique for each instance.. How to let the user know to input a unique value if he re-entered a value which resembles to a previous instance... If  i store the value in a property say HC_VALUE1, Can i  retrieve during second instance and how should i give the condition...Plz help me out.. M still a learner in Installshield.....