Hello, Alphonso!
Expression [varN01 = varP21 + varP12 + varP26] for a flow aux variable [varN01] in [Main] object does not work because
variables [varP21], [varP12] and [varP12] are not in [Main] object visibility range. These variables belong to the
instances of classes [Node01] and [Node 02]. You create an instance of an Active Object class when you drag&drop it
into another Active Object class area. Instances you created have names. By default, in your case the instances will
get the following names: [node01] and [node02]. So, the following expression must be ok:
varN01 = node02.varP21 + node01.varP12 + node02.varP26
In this expression [node02.varP21] means that variable [varP21] belongs to an instance with name [node02]. You can
rename all variables and Active Object instances by editing [Name] field in [Properties] view.

