You can compute many different (new) columns inside the same 
Calculator Action. For example, here is an example that computes the column “weight” that is the “weight of the connection between 2 individuals (A and B) inside a telecommunication network”.
As you can see in the screenshot above, the column weight is the arithmetic mean of the 2 variables “WeightAB” and “WeightBA”. These variables are defined on the other tabs inside the Calculator Action:
To be able to use the variables “WeightAB” and “WeightBA” inside the expression of the “Weight”, we must enable these 2 checkboxes:
More precisely, if you want to use a column X inside the expression of the column Y, you need to:
a)Enable the “is Input Var” checkbox inside the tab of the column X.
b)Move the tab of the column X on the left-side of the tab of the column Y. (because the different expressions are evaluated in the order from the left to the right).
Use the 2 arrows 
to re-order the tabs.
Use the 
and the 
buttons to add/remove tabs.
