Dialog menu enabling and disabling items

This is an easy question and I'm sure someone else has already asked this but I can't seem to find it so here goes.

I'm adding menus to a dialog box, I probably should have created an SDI project in the first place but its done now.  I have no problems creating the menu in the resource editor, I create a CMenu member to make life easy.  No problems adding the menu to the dialog box, it shows up quite nicely.  I use the following code in my initdialog function:

      m_File_menu.LoadMenu(IDR_FILE_MENU);
      SetMenu(&m_File_menu);
      m_File_menu.EnableMenuItem(ID_FILE_CLOSE,      MF_BYCOMMAND | MF_GRAYED);
      m_File_menu.EnableMenuItem(ID_FILE_SAVE,      MF_BYCOMMAND | MF_GRAYED);
      m_File_menu.EnableMenuItem(ID_FILE_SAVEAS,      MF_BYCOMMAND | MF_GRAYED);
      m_File_menu.Detach();

The problem occurs when later on after the user has performed an action I want to enable certain menu items and disable others.  Here's the code I'm using maybe someone can point out why this doesn't work and what I should be doing.

      m_File_menu.LoadMenu(IDR_FILE_MENU);                  
      m_File_menu.EnableMenuItem(ID_FILE_SAVEAS,      MF_BYCOMMAND | MF_ENABLED);
                m_File_menu.Detach();

If I don't "Reload" the menu the Enable crashes, but since I detached from the menu during init that makes sense.  So I try to load the menu but it always fails(returns 0).  I've tried attaching to the menu, no luck.  Any ideas?

Thanks,
Dave