It would be useful to have a method where you could specify global/environmental variables/parameters that is separate and independent from the data driven feature. These global parameters would be avalaible to all tests using the Data Driven interface of binding values to test steps, but would not be mingled in the data source itself. This way you can create a data driven test that runs iterations but keep the environmental static data e.g. userid's to login as, separate from the data itself.