Visual Basic for Applications Reference
The Nothing keyword is used to disassociate an object variable from an actual object. Use the Set statement to assign Nothing to an object variable. For example:
Set MyObject = Nothing
Several object variables can refer to the same actual object. When Nothing is assigned to an object variable, that variable no longer refers to an actual object. When several object variables refer to the same object, memory and system resources associated with the object to which the variables refer are released only after all of them have been set to Nothing, either explicitly using Set, or implicitly after the last object variable set to Nothing goes out of scope.