Go ahead an register for all the exams you desire to take.  You will obviously need to have one of your exams scheduled as an "Alternate Exam" (late testing), but this is something your school must do.  TR's system identifies all of the exam conflicts for schools allowing them to schedule one of your exams as an alternate.  Once your exam is scheduled as an alternate it will show if you reprint a confirmation  when you log in at www.Student.TotalRegistration.net