changing only selected text color not entire text in CEDIT control of mfc

void CODEdit::OnPaint()
{
	// Prepare to draw
	CPaintDC dc(this); 
	CRect rClient;
	GetClientRect(&rClient);
	DWORD dwStyle = GetStyle();
	CString cstrText;
	GetWindowText(cstrText);

	// Double buffer 
	CDC dcMem;
	dcMem.CreateCompatibleDC(&dc);
	CBitmap bmp;
	bmp.CreateDiscardableBitmap(&dc, 
		rClient.Width(), rClient.Height());
	dcMem.SelectObject(bmp);
	dcMem.SelectObject(GetFont());

	// Draw border
	CPen penBorder;
	penBorder.CreatePen(PS_SOLID, 1, m_crBorder);
	CPen* pOldPen = dcMem.SelectObject(&penBorder);
	dcMem.FillSolidRect(rClient, m_crBack);
	dcMem.Rectangle(rClient);
	dcMem.SelectObject(pOldPen);

	// Draw text
	CRect rTxt = rClient;
	UINT nFormat = DT_LEFT|DT_TOP|DT_SINGLELINE;
	// Handle margins
	DWORD dwMargins = GetMargins();
	rTxt.InflateRect(-LOWORD(dwMargins), 0, -HIWORD(dwMargins), 0);
	rTxt.InflateRect(-1,-1,-1,-1);
	// Handle selected text
	DWORD dwSel = GetSel();
	int iStartSel = LOWORD(dwSel);
	int iEndSel = HIWORD(dwSel);

	if((iStartSel == 0) && (iEndSel == 0))
	{
		// No selection, just draw
		dcMem.DrawText(cstrText, cstrText.GetLength(), rTxt, nFormat);
	}
	else
	{
		int iCurX = rTxt.left;
		int iStartChar = 0;
		int iEndChar = (iStartSel == 0 ? iEndSel : iStartSel);

		while(iStartChar < cstrText.GetLength())
		{
			CString cstrPart = cstrText.Mid(iStartChar, (iEndChar - iStartChar));

			BOOL bSel = (iStartChar == iStartSel);
			dcMem.SetTextColor(bSel ? ::GetSysColor(COLOR_HIGHLIGHTTEXT) : ::GetSysColor(COLOR_WINDOWTEXT));
			dcMem.SetBkColor(bSel ? ::GetSysColor(COLOR_HIGHLIGHT) : m_crBack);

			CRect rSel = rTxt;
			rSel.left = iCurX;
			dcMem.DrawText(cstrPart, cstrPart.GetLength(), rSel, nFormat);
			
			iCurX += dcMem.GetTextExtent(cstrPart, cstrPart.GetLength()).cx;
			iStartChar = iEndChar;
			iEndChar = ((iStartChar == iStartSel) ? iEndSel :  cstrText.GetLength());
		}
	}

	// Update the screen
	dc.BitBlt(0, 0, rClient.Width(), rClient.Height(), &dcMem, 0, 0, SRCCOPY);
}

m_crBorder		= RGB(128,160,192);
m_crBack		= RGB(255,255,255);