vxd中用怎么使用SystemParametersInfo

我用刚学vxd，用NuMega VtoolsD做了一个vxd程序，想在启动时屏蔽Ctrl+Alt+Del三个键，于是想到了SystemParametersInfo。但使用时经常出错，请各位大侠帮忙分析一下：
  struct {
long fuWinIni;
SEGOFFSET lpvParam;
long uParam;
           long uAction;
         }DisabledThreeKey;


VOID _cdecl disableCAD_Handler(PVOID RefData, DWORD flags)
{
PVOID la;
    DisabledThreeKey.uAction=36;
    DisabledThreeKey.uParam=1;
    DisabledThreeKey.lpvParam=NULL;
    DisabledThreeKey.fuWinIni=0;
_SHELL_CallDll(\"USER\", \"SystemParametersInfo\", sizeof(DisabledThreeKey), &DisabledThreeKey);
    DisabledThreeKey.uAction=97;
_SHELL_CallDll(\"USER\", \"SystemParametersInfo\", sizeof(DisabledThreeKey), &DisabledThreeKey);
}

void ExecuteCtrl_Alt_Del(void)
{
  _SHELL_CallAtAppyTime(disableCAD_Handler,(PVOID)_CREATE_, 0, 0) ;
}