Dynamically set the data source of a choice control

There are cases when the data source of a choice control depends on the value of another control on the form.

For example:
You have a multi-choice field with the associated company departments for a support request, called c_Department.
You want the user to select the primary department and store it in another field.

You create a new ComboBox control (named for example c_MainDepartment) and in the Lookup Details tab, you must set the Lookup Static Values property to :

As soon as the user sets the values inside the c_Department control, the data source of the c_MainDepartment control is updated to reflect the new data.