Diagnosis
You have tried to create an expression that already exists in thisform.

System Response
The system informs you that you are trying to create functionallyidentical expressions.

Procedure
Check whether you can use one of the existing expressions.
If you still want to create a functionally identical expression, thisis possible. You might want to do so if you want to use thedocumentation in a different way than is the case with the existingexpression.