If the RowSource of the ComboBox has multiple columns (and the ColumnCount >
1) then the BoundColumn property determines which column from the RowSource
will become the Value of the ComboBox and if the ComboBox is bound to a
field in a bound form then that is the value that gets written to the table.
For example it would be a common approach to have a ComboBox display an
EmployeeName while storing an EmployeeNumber. In that case the if the
RowSource was...
SELECT EmployeeName, EmployeeNumber FROM Employees
....the BoundColumn would be set to 2 to make the EmployeeNumber be the value
saved to the table.