Reference/SendMessage

SendMessage

HWND msg wparam lparam [user_var(return value)] [/TIMEOUT=time_in_ms]

Sends a message to HWND. If a user variable $x is specified as the last parameter (or one before the last if you use /TIMEOUT), the return value of SendMessage will be stored to it. Note that when specifying 'msg' you must just use the integer value of the message. If you wish to send strings use "STR:a string" as wParam or lParam where needed.

WM_CLOSE 16
WM_COMMAND 273
WM_USER 1024

Include WinMessages.nsh to have all of Windows messages defined in your script.

To send a string param, put STR: before the parameter, for example: "STR:Some string".

Use /TIMEOUT=time_in_ms to specify the duration, in milliseconds, of the time-out period.

!include WinMessages.nsh
FindWindow $0 "Winamp v1.x"
SendMessage $0 ${WM_CLOSE} 0 0

Command introduced with NSIS v1.51