Call this function to retrieve the OLE item's size.
This function provides the same information as GetExtent. However, you can call GetCachedExtent to get extent information during the processing of other OLE handlers, such as OnChange. The dimensions are in MM_HIMETRIC units.
This is possible because GetCachedExtent uses the IViewObject2 interface rather than use the IOleObject interface to get the extent of this item. The IViewObject2 COM object caches the extent information used in the previous call to IViewObject::Draw.
For more information, see IViewObject2::GetExtent in the Windows SDK.