Here dimensionMenu points to the AcadPopupMenu representing the Dimension Menu.
The code adds a submenu (camSubMenu) and several menu entries into it. As for the events, you'll have to play with the items returned by the AddMenuItem methods.
[code]
AcadPopupMenu camSubMenu = dimensionMenu.AddSubMenu(dimensionMenu.Count, "CAM Dimensions");
camSubMenu.AddMenuItem(dimensionMenu.Count, "Square", "SQUAREDIM ");
camSubMenu.AddMenuItem(dimensionMenu.Count, "Sphere Radius", "SPHERERADIUS ");
camSubMenu.AddMenuItem(dimensionMenu.Count, "Sphere Diameter", "SPHEREDIAMETER ");
camSubMenu.AddMenuItem(dimensionMenu.Count, "Key", "KEYDIM ");
camSubMenu.AddMenuItem(dimensionMenu.Count, "Leader", "LEADERDIM ");
[/code]