Defines a user-defined function to be called when a tray item is clicked.
TrayItemSetOnEvent ( itemID, "function" )
| itemID | The item identifier (itemID) as returned by a TrayCreateItem function. | 
| function | The name of the user function to call. | 
| Success: | 1. | 
| Failure: | 0. | 
| @error: | 1 = the "function" is not defined. | 
OnEvent functions are only called when the option Opt("TrayOnEventMode", 1) - when in this mode TrayGetMsg() is NOT used at all.
Within the called user function the item identifier can be retrieved with @TRAY_ID.
If the function is an empty string "" the previous user-defined is disabled.
TrayCreateItem, TrayGetMsg, TrayOnEventMode (Option), TraySetOnEvent
#NoTrayIcon
#include <MsgBoxConstants.au3>
#include <StringConstants.au3>
#include <TrayConstants.au3>
Opt("TrayMenuMode", 3) ; The default tray menu items will not be shown and items are not checked when selected. These are options 1 and 2 for TrayMenuMode.
Opt("TrayOnEventMode", 1) ; Enable TrayOnEventMode.
Example()
Func Example()
    TrayCreateItem("About")
    TrayItemSetOnEvent(-1, "About")
    TrayCreateItem("") ; Create a separator line.
    TrayCreateItem("Exit")
    TrayItemSetOnEvent(-1, "ExitScript")
    TraySetOnEvent($TRAY_EVENT_PRIMARYDOUBLE, "About") ; Display the About MsgBox when the tray icon is double clicked on with the primary mouse button.
    TraySetState($TRAY_ICONSTATE_SHOW) ; Show the tray menu.
    While 1
        Sleep(100) ; An idle loop.
    WEnd
EndFunc   ;==>Example
Func About()
    ; Display a message box about the AutoIt version and installation path of the AutoIt executable.
    MsgBox($MB_SYSTEMMODAL, "", "AutoIt tray menu example." & @CRLF & @CRLF & _
            "Version: " & @AutoItVersion & @CRLF & _
            "Install Path: " & StringLeft(@AutoItExe, StringInStr(@AutoItExe, "\", $STR_NOCASESENSEBASIC, -1) - 1)) ; Find the folder of a full path.
EndFunc   ;==>About
Func ExitScript()
    Exit
EndFunc   ;==>ExitScript