Indicate to which data table expressions in a drop-down are related to

When creating the calculated value you can select which data table it should be referencing, this will make the value to appear empty depending on which expression is selected from the drop-down. By design the calculated value will depend on the data table selected, so when you select from the drop-down an expression that does not reference the same data table as the selected in the calculated value settings, the empty (----) result will be displayed. When both, the drop down selection and the calculated value, reference the same data table the result is valid. It would be useful to know to which data table the expressions are referencing  to when using a drop-down.