How to set a starting root directory for this code that selects a folder name?

[Mike Pliam]

The following code is useful to allow a user to select a particular folder in the disk directory.

void OpenFolder()
{
	LPMALLOC pMalloc; //,pMalloc2;
	CString strDirectory;
	BROWSEINFO bi;
	// Gets the Shell's default allocator
	wchar_t pszBuffer[MAX_PATH];
	LPITEMIDLIST pidl;
	// Get help on BROWSEINFO struct - it's got all the bit settings.
	bi.hwndOwner = ::GetDesktopWindow();
	bi.pidlRoot = NULL;
	bi.pszDisplayName = pszBuffer;
	bi.lpszTitle = _T("Select A Directory");
	bi.ulFlags = BIF_RETURNFSANCESTORS | BIF_RETURNONLYFSDIRS | BIF_NEWDIA********;
	bi.lpfn = NULL;
	bi.lParam = 0;

            
	if (::SHGetMalloc(&pMalloc) == NOERROR)
	{
		if ((pidl = ::SHBrowseForFolder(&bi)) != NULL)
		{
			if (::SHGetPathFromIDList(pidl, pszBuffer))
			{ 
				strDirectory = pszBuffer;
			}
			pMalloc->Free(pidl);
		}
		pMalloc->Release();
	}

	TRACE0("strDirectory =: "); 
	OutputDebugString(strDirectory); TRACE0("\n");

}

However, if one uses this code over and over, one quickly becomes tired of threading one's way all the way from root directory C:\. There is undoubtedly some way to designate a starting directory. The most obvious candidate to set such a target is the:

bi.pidlRoot = NULL;

But attempting to set bi.pidlRoot to a CString (directory address) errors because 'no suiitable conversion from CString to LPCITEMIDLIST exists'

How can I set the code to open at a designated address in the directory tree?