Based on the title of your question, not the body, I THINK you are asking how to bill a visit on additional days if the patient was admitted, but still physically located in the ER because no IP beds were available. If so, that is coded exactly the same as if the pt was in an IP bed. Hospital coding is based on the status of the patient, not the physical location of the patient.
If that doesn't help answer your question, please clarify what you are asking.