Why would USER B entering data whild USER A is logged in be a problem? The data can be entered into a global field and scripts that "run with full access privileges" can still access the data for USER B if that should be necessary.
Essentially the physician would view the image on a computer station on a simulation room monitor where he would then need to electronically "signoff" on the image. This image will be prepared for him to see via a different user account (a therapist's account). I need a way to verify against the physician account because the therapist will still be logged in. I know it sounds goofy but some of our doc's come in and out of the room in less than a minute sometimes.
We use a medical records system that lets you record your 'signature' with a PIN. That doesn't require true FM re-log in (although that is very fast, anyway). You just click the button and sign in with your PIN, and now we know who you are, so you just click an 'Approved' button or whatever and it records your name. It is as fast as typing a few numbers. One click logs out of you PIN and away you go.
(Note that you don't actually want the user name, you want the account name.
That's exactly what I understood you to mean. I don't see why you have to change the log in just to capture the doc's signature.
Collect the signature in a global field. Identify the Doc by selecting a name from a value list set up on another global field. Click a button or trip a script trigger that then logs/verifies this info as needed. The scripts need not be restricted by your current user's privilege set limits as the script can be set to run with full access privileges.