I like to be able to call an "autohotkey" executable message box from within a running Cache routine executing as a jobbed routine. The autohotkey executable displays a small pop-up window with a message and an "OK" button .. and will time out in 10 seconds if the user does not press the OK button.

Although $ZF(-1,cmd) executes (where "cmd" contains a simple batch command e.g. @c:\autohotkey\warning.exe), no interactive window appears and, once the autohotkey routine times out, the calling cache routine simply continues.