Send Message

Sends the specified message to a window or windows. The SendMessage function calls the window procedure for the specified window and does not return until the window procedure has processed the message.

Syntax :

LRESULT WINAPI SendMessage(

    HWND hWnd,

    UINT Msg,

    WPARAM wParam,

    LPARAM lParam

);

Parameters:

hWnd [in]

Type: HWND

A handle to the window whose window procedure will receive the message. If this parameter is HWND_BROADCAST ((HWND)0xffff), the message is sent to all top-level windows in the system, including disabled or invisible unowned windows, overlapped windows, and pop-up windows; but the message is not sent to child windows.

Msg [in]:

Type: UINT

The message to be sent.

wParam [in]

Type: WPARAM

Additional message-specific information.

lParam [in]

Type: LPARAM

Additional message-specific information.



Source:MSDN