Chen, you could do something like this in your business object that returns your list of employee names:

   Public Function GetEmployeeNameList(ByVal dataOwnerID As Integer) As DataSet

        ' Get a reference to the data access object
        Dim dao As mmDataAccessBase = Me.GetDataAccessObject()

        ' Build the SQL command string
        Dim mySql As String
        mySql = "SELECT EmployeeID, (NameFirst + ' ' + NameLast) AS EmployeeName From Employee"

        ' Get a DataSet filled with the result set
        Return Me.GetDataSet(mySql)

Then set you BindingSourceDisplayMember to the EmployeeName column in the dataset returned by you business object.