You attempted to perform an operation that is exclusive to Collection objects, on an object that is not a Collection object. Some properties, methods, and operations only apply to Collection objects. A Collection object is an object that contains a set of related objects. An object's position within a Collection object can change whenever a change occurs in the collection; therefore, the position of any one object in the Collection object may vary.
To correct this error
Check the spelling of the object or property name.
Verify that the object is a Collection object.
Look at the Add method used to add the object to the collection to be sure the syntax is correct and that any identifiers were spelled correctly.