DocumentProperties调用不成功，求大侠帮忙

[lwing25]

代码如下：

HANDLE hPrinter;
if (!::OpenPrinter( CT2W(lpszPrinterName), &hPrinter, NULL))
{
return;
}
HWND hWnd = ::GetActiveWindow();
//这里的nDevModeSize 返回8752
LONG nDevModeSize = ::DocumentProperties(hWnd, hPrinter, CT2W(lpszPrinterName), NULL, NULL, 0);
LPDEVMODE pDevMode = (LPDEVMODE)malloc(nDevModeSize);

//这里nRes一直返回-1
LONG nRes = ::DocumentProperties(hWnd, hPrinter, CT2W(lpszPrinterName), pDevMode, NULL, DM_OUT_BUFFER);
DWORD dwErr = 0;
if (nRes < 0)
{
//拿到的dwErr为0
dwErr = GetLastError();
}
free((VOID *)pDevMode);