keybd_event(18,0,KEYEVENTF_KEYUP,0);

另外，keybd_event的函数原型为：

VOID WINAPI keybd_event(   _In_  BYTE bVk,   _In_  BYTE bScan,   _In_  DWORD dwFlags,   _In_  ULONG_PTR dwExtraInfo );

第二个参数是scancode(扫描码)。由虚拟按键得到扫描码使用函数MapVirtualKey。MapVirtualKey还可以由扫描码得到虚拟按键编码。

UINT WINAPI MapVirtualKey(   _In_  UINT uCode,   _In_  UINT uMapType );

Parameters     uCode [in] Type: UINT     The virtual key code or scan code for a key. How this value is interpreted depends on the value of the uMapType parameter. uMapType [in]     Type: UINT     The translation to be performed. The value of this parameter depends on the value of the uCode parameter. Value                                   （1）MAPVK_VK_TO_CHAR  2 uCode is a virtual-key code and is translated into an unshifted character value in the low-order word of the return value. Dead keys (diacritics) are indicated by setting the top bit of the return value. If there is no translation, the function returns 0. （2）MAPVK_VK_TO_VSC    0 uCode is a virtual-key code and is translated into a scan code. If it is a virtual-key code that does not distinguish between left- and right-hand keys, the left-hand scan code is returned. If there is no translation, the function returns 0. （3）MAPVK_VSC_TO_VK   1 uCode is a scan code and is translated into a virtual-key code that does not distinguish between left- and right-hand keys. If there is no translation, the function returns 0. （4）MAPVK_VSC_TO_VK_EX   3 uCode is a scan code and is translated into a virtual-key code that distinguishes between left- and right-hand keys. If there is no translation, the function returns 0.

The return value is either a scan code, a virtual-key code, or a character value, depending on the value of uCode and uMapType. If there is no translation, the return value is zero.