ComboList Control Attribute
If the ComboList Control bit is set on a combo box, the edit field is replaced by a static text field. This prevents a user from entering a new value and requires the user to choose only one of the predefined values.
If this bit is not set, the combo box has an edit field.
To set this attribute on a control, include the ComboList bit in the Attributes column of the control's record in the Control table.