event add <<virtual>> sequence ?sequence ...?
event delete <<virtual>> ?sequence sequence ...?
event generate window event ?option value option value ...?
event info ?<<virtual>>?
http://purl.org/tcl/home/man/tcl8.4/TkCmd/event.htm
Tested to work on Windows:
event generate . <Alt-F4> ;# sudden death, somehow like [exit]
However, other Alt-(initial) events don't work when called from event, only from the keyboard.
See also:
Tk syntax help - Arts and Crafts of Tcl-Tk Programming - Category Command