I had vacation in week 1 of March. I did just what you want to do. I slid my vacation back 2 days into Feb to conflict with a trip and then I expanded beyond my vacation foot print into March. Be careful with the total credit hour math, though. I missed knocking out one trip that I planned to knock out because I was over the credit hour limit to expand (6 hours above the scheduled vacation value) by a few minutes. My mistake, but I was still able to do just what you want to do.