I want that my calculated multibox should always have one value selected.
I tried by replacing it with a normal field, checking the 'always one selected value' in presentation, and then again replacing it with the calculated field.
The "Always one selected value" setting is a property of the field in a list/multibox, and not a property of the box. You can see this by creating two list boxes referencing the same field. If you change the setting in one, then the other also changes.
Because it is a property of a field, "Aways one selected" cannot be applied to an expression. You have two options:
Fiddle about with selection triggers and actions/macros to manually enforce the condition.
Create the values as a field in the script so you don't use an expression
Logic will get you from a to b. Imagination will take you everywhere. - A Einstein
