Subclassing CCombobox (problem)!!

Visual C++ 1.52

I have a CCombobox ctrl(drop list) in a dialog(savedlg) derived from CFiledialog . I have subclassed this CCombobox to Mycombo derived from CWnd in order to catch the OnRButtondown and OnRButtonup
events. In savedlg.h I have created

CMycombo m_mycombo;

In savedlg.cpp 's OnInitdialog()

m_mycombo.SubclassDlgItem(IDC_COMBOBOX,this); //line 2

Everything works fine and the events are caught as expected but when I close the savedlg and come back to my mainwindow and click on any of the menu items then the toolhelp that pops up at the bottom of my main window (remember I am working in VC++ 1.52!!!!!!!!!!!!), gets overwritten one on top of the other as I go over the menu items and results in a thick black line finally. I created the savedlg's combobox in Appstudio . If I comment this line 2 then the above problem does not occur. Anyone has any clue as to why this would happen.

Thank You
sab.