Yes, you only get one chance to set the user name when you first set up a user. Luckily for me, I realized this while I was trialing AC, before I set up our real database. So, I set up our users with our 3 letter initials, which is also how we sign messages. First names only seem too casual for a medical record to me. It is also unlikely that we will ever duplicate 3 letter sequences, so it will be easy to identify specific personnel.