VC中使用WebBrowser怎么模拟网页的onMouseDown事件

VC中使用WebBrowser如何模拟网页的onMouseDown事件
先用get_onmousedown,再用Invoke应该是对的呀，返回值hresult竟然是E_INVALIDARG
代码如下：

VARIANT varMouseDown;
varMouseDown.vt = VT_DISPATCH;
pElement->get_onmousedown(&varMouseDown);
IDispatch *pDispMouseDown;
pDispMouseDown = varMouseDown.pdispVal;

HRESULT hresult;
hresult = pDispMouseDown->Invoke(0, IID_NULL, 0, DISPATCH_METHOD, 0, NULL, NULL, 0);
int itest = 0;

------解决方案--------------------
VariantInit没调用，鬼知道里面有什么
------解决方案--------------------
http://www.codeproject.com/Articles/4805/Advanced-customization-of-WebBrowser-Control-in-Di


Advanced customization of WebBrowser Control in Dialog based app.
------解决方案--------------------
varMouseDown.vt = VT_DISPATCH这一行去掉，你设置了dispatch一定要设置lpdispatch的，不然就不匹配了