There are a few dialog boxes that don't fit into the normal sequence of wizard pages but represent errors or similar out-of-sequence conditions. We can specify them using the OnExit
attribute in the Show
tag used for scheduling. The value can be success, cancel, error or suspend:
<InstallUISequence>
<Show Dialog="FatalError" OnExit="error" />
<Show Dialog="UserExit" OnExit="cancel" />
<Show Dialog="ExitDialog" OnExit="success" />
...
</InstallUISequence>