You're either not keeping the min number of on call days (3 or 4) or exceeding the max number of off day blocks. You can only move days from the end of a reserve block, not the middle. Also, you can't break the min on call day requirement at the end of the month during PCS. Sometimes it takes me multiple PCS's to accomplish what I want. Also, if your category has MSL, you can't break that. I'm not sure we h currently have any categories with MSL...usually the 350.