Where are you entering data? A Form or a table?
Usually data is entered into a form and this is by way of a text Box Control which may or may not be bound to a Table or Query.
You can have two Controls on the same form to both show the same result, not sure why though.
You can also have a Form and Subform where data is replicated.
Unbound text box controls on forms can have their control source to be another control.
Often this is a Calculated Control where a Sum or an Addition or subtraction is performed eg QtySold & ItemPrice on a Form plus a control that has =[QtySold]*[ItemPrice] as it's control source.