I'm afraid not. The whole Rollback scenario get's complicated once Custom Actions are introduced. The installer (from what I know) just processes the value the Custom Action returns and decides to either stop or continue. The Windows Installer says the way around this would be tu use something called a "Rollback Custom Action". This is an advanced type and is exposed in InstallShield Developer. You might want to do a bit mroe research on this though because my knowledge of the subject is rather limited.
Chandima Rajakaruna
Macrovision Corporation