How to work with doublebufferpaintevent in C++?

void CDeWarp::DoubleBufferPaintDewarppreviewer(long Hdc)
{
	VARIANT_BOOL bLoaded;
	m_piUnchangedPreview->get_IsLoaded(&bLoaded);
    if(bLoaded)  // there is something in the viewer
	{

        //Attach Graphics to the temporary DC (control's double buffer)
		// HOW TO DO THIS IN C++?
		//objGraphics.Hdc = Hdc 
        //Adjust pen and brush // HOW TO DO THIS IN C++?
		//objGraphics.Pen.ForeColor = &HFFFF0000
		//Scale pen weight proportionally to zoom
		//objGraphics.Pen.Weight = 2

        //Recalculate anchor points from bitmap coordinates to the control ones
		long i;
        long arrControlPointX[4], arrControlPointY[4];
        for (i=0;i<4 ;i++ )
		{
			piPreviewBox->BitmapToControlXCoord(arrSrcPointX[i],&arrControlPointX[i]);
			piPreviewBox->BitmapToControlXCoord(arrSrcPointY[i],&arrControlPointY[i]);
		}


        //Draw fitting quadrangle - LEAVES LINES ALL OVER THE BITMAP
		m_piPreviewGraphics->DrawLine(arrControlPointX[0], arrControlPointY[0],
            arrControlPointX[1], arrControlPointY[1]);

        m_piPreviewGraphics->DrawLine(arrControlPointX[1], arrControlPointY[1],
		arrControlPointX[2], arrControlPointY[2]);

        m_piPreviewGraphics->DrawLine(arrControlPointX[2], arrControlPointY[2],
            arrControlPointX[3], arrControlPointY[3]);

        m_piPreviewGraphics->DrawLine(arrControlPointX[3], arrControlPointY[3],
            arrControlPointX[0], arrControlPointY[0]);

        //Draw anchor points
       for(i=0; i<4; i++) 
		m_piPreviewGraphics->DrawRectangle(arrControlPointX[i] - 3, arrControlPointY[i] - 3, 7, 7, FALSE, TRUE,0);
	} //end .isloaded
	piPreviewBox->put_AutoUpdate(FALSE);
}