"Installed" condition not working in custom actions.

I have a installscript function which executes before "RegisterUser" custom action.

Condition given to this custom action is "Installed", such that my script should not execute during first time installation or un-installation.

But for me this script is never executing. My product is already installed. Next time when I install the product, I want this script to execute. But it is not executing. Am I missing something?