Allow user to cancel during install?

[Wasteland]

Once the installer has started copying files, it seems the cancel button becomes disabled, and it does not let a user cancel the install unless something goes wrong (in which case it displays an error and enables the cancel button). Is there some way I can tell NSIS to always have the cancel button enabled? If I just send the windows message to enable the button, is the installer going to function correctly (i.e. stop if a user hits cancel), or does it expect the cancel button to stay disabled?