Helper variable that controls if cancellation is allowed while the installation is in progress. In practical terms, this variable controls the Cancel button on the predefined ProgressDlg dialog box: if nonzero, the Cancel button is enabled and the user can cancel the installation; if zero, the button is disabled.
Note: By default, this variable has no effect on dialog boxes that are shown prior to the progress dialog; the user can always cancel the installation at those points. If you want to use UIAllowCancel in other dialog boxes as well, you should specify it in the Condition field of the appropriate Cancel buttons. Refer to the predefined ProgressDlg dialog box for an example.
Tip: For more information about the Cancel mechanism, see How the Cancel button works.
You can refer to this variable as <UIAllowCancel>. In conditional expressions you can omit the brackets and use tests like UIAllowCancel. You should set this variable to 1 or 0 to enable or disable use of the Cancel button while the installation is in progress. You can also use a Set Variable action to change its value at installation time.