Using IMH for this may be problematic mainly because of the idea of using "Open" email. Of course, you could encrypt the messages. Just the HIPAA issues. But the questioning could be ok for this purpose. RelayHealth and Medem both offer facilities for this with "secure messaging."
@Bert: I get what you mean concerning the second message. Let's say if you receive an additional question about a previous (recent) Online consult as in your example, you have a lesser "Online Follow-up" fee. You pick the follow-up fee. I'm really interested in what people think is a proper fee assuming that you feel it is appropriate to address the issue online at all. If you don;t, you respond appropriately (You must come in for this, go to ER immedialtely!, etc)and don't charge the fee.
For example, you receive a request for the online consult. They are complaining of UTI symptoms. They asswer some questions (pre-set and online)concerning their symptoms. You agree to do this one. What do you feel is the appropriate charge?