Calling acPreviousApplication() multiple times will switch the focus between all opened windows in a row starting from the last active and ending with the first active.
I am unable to reproduce that. It only switches between the last 2 on my system (Win 8 64).
I can't use acSendKeys("%{Tab}"), because it doesn't work in Windows 8.
This seems to work for me in Windows 8:acSendAltDown()
acDelay(25)
acSendKeys("{TAB}")
acSendAltUp()
Another problem with acPreviousApplication() is that it doesn't work if the gesture/modifier click is performed in the task bar.
I can't reproduce this either; well, after disabling the Taskbar ignored window, that is.