ArgoUML operations

I created an ERD (entity relationship diagram) using ArgoUML, and I want to create two operations inside a class that have a return type void. However, I can only create one operation that returns a type void.

For instance:

I can set the return type bookInitial()to void, but whenever I try to set the return type bookFollowUp()to void, this option is not available.

When checking with other classes in the project, it would seem that each class allows only one object to have a return type void- is this true for all classes?

Is there a way to assign a return type to voidmore than one operation?

Thank.