Is there any way to update variables that are functions of another, if the original variable Y has been amended or updated . The former is straightforward to edit Y's values. But I am not clear that for example, l-Y  is automatically recalculated. And if  l-Y  has already been used in a session, Gretl will not let it be deleted giving the error message cannot be deleted variable in use.. 

Suggestions around this issue welcomed