// This OnSize function resizes one large control in a dialog. 
// The one control grows horizontally and vertically to fill the dialog. It's position remains unchanged.
// Other controls (buttons etc) would typically be above the one resizable control.
// How to add OnSize:
// [1] add to .h:                     afx_msg void OnSize(UINT nType, int cx, int cy);
// [2] add to message map in .cpp:    ON_WM_SIZE()
// [3] add this OnSize function.
void CMyDlg::OnSize(UINT nType, int formWidthArg, int formHeightArg)
{
   CDialog::OnSize(nType, formWidthArg, formHeightArg); // Let dialog resize itself.
 
   // http://www.codersource.net/mfc_resize_controls.html
   // http://wwwusers.brookes.ac.uk/p0071643/resize.htm
 
   // get pointer to the control to be resized dynamically
   CWnd* pCtl = GetDlgItem(IDC_MSFLEXGRID1);
 
   if (!pCtl) { return; } // control may not exist yet.
 
   CRect rectCtl;                 // Allocate CRect for control's position.
   pCtl->GetWindowRect(&rectCtl); // Get control's position.
   ScreenToClient(&rectCtl);      // Convert from absolute screen coordinates to dialog-relative coordinates.
 
   // Now resize the control dynamically by calling MoveWindow
   // rectCtl.left is assumed to be the left, bottom and right margin for the control. 
   pCtl->MoveWindow(
      rectCtl.left,                               // x. remains unchanged
      rectCtl.top,                                // y. remains unchanged
      formWidthArg - 2 * rectCtl.left,            // w. Grow to fill horizontally
      formHeightArg - rectCtl.top - rectCtl.left, // h. Grow to fill vertically
      TRUE)
   ;
 
   return;
} // OnSize()