When the enabled property of one combobox is modified between true and false it is modified for one textbox.

Combobox properties:
- DropDownStyle: DropDownList
- AutoCompleteMode: Append
- AutoCompleteSource: ListItems
- FormattingEnabled: True
- PopulationType: BusinessObject
- PopulateOnFormLoad: Manual
- TopMostDescription: "<.... a text ...>"
- TopMostValue: -1
- ValueMemberDataType: Object

After choice of an option (Operação):