Launch application inside dialog window

I'm trying to preview a screensaver inside a dialog window (much like the preview inside the Display Properties).  I need to launch the Screensaver with the arguments "/p ####", where #### is the HWND of the window to launch in (I'm just wanting to launch it in an MFC text control).  I can do the provew with my own screensaver that I wrote (I've got the CWnd class), but I want to actually launch an executable in there.  I've tried ShellExecute and CreateProcess without luck, but I dont know how to translate the HWND to the command line.  Any help?
lakers2003Asked:
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AlexFMCommented:
You can use Format function to convert HWND to string:
CString s;
s.Format(_T("%x"), (int)hWnd);

Inside of screen saver, if you have, for example, command line parameter "A56B", you can extract it from string:

int n;
_stscanf(sParameter, _T("%x"), &n);
HWND hWnd = (HWND)(DWORD)n;
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migelCommented:
Hi!
as MSDN say:
<HWND> is a HWND presented on the command line as an unsigned decimal number.
so you can just use wsprintf to get this:
for example
TCHAR tchCmdLine[_MAX_PATH];
wsprintf(tchCmdLine, _T("/p %u"), m_hWnd);
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lakers2003Author Commented:
That doesn't seem to work, this is what I'm doing:

HWND prevHwnd=(HWND)::GetDlgItem((HWND)AfxGetMainWnd(),(int)GetDlgItem(IDC_PREVIEW));
      
CString s;
s.Format((_T("%x"), (int)prevHwnd));

CString m_ssProcess = "C:\\WINDOWS\\system32\\sspipes.scr /p ";
    BOOL cres=CreateProcess(m_ssProcess,NULL,0,0,FALSE,            CREATE_NEW_PROCESS_GROUP|CREATE_DEFAULT_ERROR_MODE,0,"C:\\WINDOWS\\system32",&si,&pi);
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lakers2003Author Commented:
The code fails before it gets to the CreateProcess block.
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lakers2003Author Commented:
Ok, I think migel's solution worked to get the HWND, but do I need to set any other parameters to preview the screen saver in the dialog window?  IDC_PREVIEW is the id of the TextControl I want the preview to appear in.  Now my CreateProcess is failing...

HWND prevHwnd=::GetDlgItem(this->GetSafeHwnd(), IDC_PREVIEW);

TCHAR tchCmdLine[_MAX_PATH];
wsprintf(tchCmdLine, _T("/p %u"),prevHwnd);
CString s(tchCmdLine);
CString m_ssProcess = "C:\\WINDOWS\\system32\\sspipes.scr " + s;

BOOL cres=CreateProcess(m_ssProcess,NULL,0,0,FALSE,
            NULL,0,"C:\\WINDOWS\\system32",&si,&pi);
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