IShellFolder SelectItem

[reachb4]

I need to select all jpeg files in a folder when user presses a keyboard button after selecting any one of the jpeg files. I used IFolderView::SelectItem to select files. I used IShellFolder::ParseDisplayName() function to get pidl of the candidate files which need to be selected. The
problem is that ParseDisplayName is always failing. HRESULT says it is
because "a null reference pointer is passed into the stub". I am
getting proper value in *psf. Please tell me why is it happening so?

 IShellFolder *psf;
                       if (SUCCEEDED(ppf2->QueryInterface
(IID_IShellFolder,(void**)&psf))) {

 HRESULT hr = psf->ParseDisplayName(NULL,NULL,g_szPath,NULL,pidlSelected,NULL);

}

Regards,
J