how to change a dialogbar size

Let m_wndControlBar is your Control Bar then, In OnCreateof your CFrameWnd add this lines after creating m_wndControlBar(May be at the end of the function).

m_wndControlBar.EnableDocking(CBRS_ALIGN_ANY);               //Enable ControlBar Docking
EnableDocking(CBRS_ALIGN_ANY);                               //Enable Docking in Main Frame
DockControlBar(&m_wndControlBar, AFX_IDW_DOCKBAR_BOTTOM);    //Call this function on any control bar to change the docking position of control bar.

Check MSDN for full info.

thanks
but i already tried this method.actually my requirement is launch the dialog initially at docked state on the right bottom of the main window.
please help me