Cannot automate/simulate listview click of another process

[Haroonrulz]

I am developing an automation tool. I want to click listview item of another process programatically. I have partially succeeded in doing. But I am getting a slightly different output.I have used NMITEMACTIVATE(I have also used PostMessage Instead of SendMessage in the code below).
C++,Win32
Small code detail:

NMITEMACTIVATE nmbh;
nmbh.hdr.code = NM_DBLCLK;
nmbh.hdr.hwndFrom=g_hWnd;
nmbh.hdr.idFrom=GetDlgCtrlID(g_hWnd);
nmbh.iItem=itemval;
nmbh.iSubItem=0;
nmbh.uNewState=0;
nmbh.uOldState=0;
nmbh.uChanged=0;
nmbh.uKeyFlags=0;
SendMessage(GetParent(g_hWnd), WM_NOTIFY,(WPARAM)g_hWnd,(LPARAM)&nmbh);