imcffp,
You can do that right now. You use the "Other Billing Info" button.
Problem is, when you export your claim, the admit/discharge dates are magically missing. Same goes for CLIA numbers. You can enter them, but they do not export (at least not in the Preferred_1500 format).
About the only thing that goes through is the name of a referring provider.
I've asked when this will be fixed, and have been told it's not a priority.
If anyone knows where the script is that generates the export, I'd like to have a friend look at it.