C#

public bool PreFilterMessage(ref Message m)
            {
                if (m.Msg == WM_NCLBUTTONDOWN)//WM_NCLBUTTONDOWN = 0xA1
                {
                    //Tell the user that, the mouse pressed
                    //the window title bar.
                    return false;
                }
                else if (m.Msg == WM_NCLBUTTONUP)//WM_NCLBUTTONUP = 0xA2
                {
                    //Tell the user that, mouse released
                    //on the window title bar.
                    return false;
                }
                return false;
            }

The WM_NCLBUTTONUP message is posted when the user releases the
left mouse button while the cursor is within the nonclient area of a window.
This message is posted to the window that contains the cursor.
<big><code>If a window has captured the mouse, this message is not posted.</code></big>

public bool PreFilterMessage(ref Message m)
            {
                if (m.Msg == WM_NCLBUTTONDOWN)//WM_NCLBUTTONDOWN = 0xA1
                {
                    //Tell the user that, the mouse pressed
                    //the window title bar.
                    <code>return true;</code>
                }
                else if (m.Msg == WM_NCLBUTTONUP)//WM_NCLBUTTONUP = 0xA2
                {
                    //Tell the user that, mouse released
                    //on the window title bar.
                    return false;
                }
                return false;
            }

Sojaner!