WinCE 6.0 施用keybd_event无法输入字符

WinCE 6.0 使用keybd_event无法输入字符
环境 TCC8900 官方V2.0版本BSP，WinCE6.0
使用扫描式键盘，驱动中通过keybd_event模拟按键消息：
发现上下左右确认等功能按键可以使用，如‘1’，‘a’等字符无法输入。
 使用MFC编写代买，定时发送'a',在VS2005自带CE虚拟机上可以正常将‘a’输入到焦点处，下载到CE设备上依然有问题
 使用USB远程桌面，同样也不能输入字符，而功能键正常。

驱动相关代码如下：

void KEY_SendEvent(int CurrentKey)
{
unsigned int timetick;

if(CurrentKey > 0) // Key pushed down
{
CurrentState = PRESSED;

timetick = GetTickCount();

if( (PreviousKey == CurrentKey) && ( (timetick - lasttick)<KEY_REPEAT_TIME) )
return ;// same key is pressed for a long time

keybd_event(CurrentKey,0,0,0); // If the second param is not specified, the key is being pressed.
RETAILMSG(1,(TEXT("[KEY ] Key %d Pressed\r\n"),CurrentKey));
lasttick = timetick;
PreviousKey = CurrentKey;

PreviousState = CurrentState;
return;
}
else // Key Release
CurrentState = RELEASED;


if( PreviousState == PRESSED) {
keybd_event(PreviousKey, 0, KEYEVENTF_KEYUP,0);
RETAILMSG(1,(TEXT("[KEY ] Key %d Released\r\n"),PreviousKey));
}

PreviousState = CurrentState;
PreviousKey = CurrentKey;
}

.bib文件
tcc_keypad.dll $(_FLATRELEASEDIR)\tcc_keypad.dll $(XIPKERNEL) SHK


请问诸位有没有遇到过类似情况，如何解决，先谢过。

------解决方案--------------------
PRESSED和RELEASED是不是配合使用的？
if
keybd_event(CurrentKey,0,0,0); 
else
keybd_event(PreviousKey, 0, KEYEVENTF_KEYUP,0);

有问题吗？