You have a complicated expression.
Put the result of the expression, or parts of the expression, in a temporary variable with a name that explains the purpose.
This refactoring is the opposite of Inline Temporary Variable
To introduce an explaining variable, highlight the expression that you wish to assign to the explaining variable and invoke Introduce Explaining Variable from the Castalia Refactoring menu.
Castalia will add a new variable to the method, attempting to determine the type of the variable. If Castalia cannot determine the appropriate type for the variable, it will declare it as Variant. You may need to change the type manually.
After adding the new variable, Castalia will create an initialization statement that assigns the value of the expression to the variable. It will replace the highlighted expression with the new variable.
Finally, Castalia will allow you to rename the variable, propogating your changes as appropriate.
To finish, press Enter. Don't forget to check the variable type for accuracy.
See also: Refactoring Overview, Inline Temporary Variable