In other words - you will be sailing 14 nights with Celebrity but won't get any credit toward your Diamond Status with Royal Caribbean. The only way to attain Diamond Status is to sail with Royal Caribbean. The same scenario applies for loyal passengers of Celebrity when they sail with Royal Caribbean. You need 80 points to become a Diamond Member. If you book a Junior Suite or higher you will earn an extra point for each day you sail. I don't know how important it is to you to make the Diamond Status, but you may want to consider those 14 points before you book.