How to change the Backlight Brightness Windows CE c# ?

void static  AdjustBrightness(BYTE bBrightNess)
{
    bool bRet = FALSE;
    HANDLE hDevBKL;    
    DWORD dwPercent=(DWORD)bBrightNess*6.4;          //3;
    hDevBKL = CreateFile(_T("BKL1:"),
                         GENERIC_READ|GENERIC_WRITE,
                         FILE_SHARE_READ|FILE_SHARE_WRITE,
                         NULL,
                         OPEN_ALWAYS,
                         0,
                         0);
        
    bRet = DeviceIoControl(hDevBKL,
                       IOCTL_BKL_SET_INTENSITY,
                       &dwPercent,
                       sizeof(dwPercent),
                       NULL,
                       0,
                       NULL,
                       NULL);
        

    if(!bRet)
    {
            SetLastError(GetLastError());
    }