Replace disk in RAID

I had a RAID array setup with 4 1tb disks. I wanted to replace each disk in the array one by one as to not go through the trouble of restarting from scratch but I can't seem to find the option. When I go to the RAID options it looks like it's going to wipe my RAID disks to build a new array but obviously this wouldn't be what I want. Maybe I'm missing some obvious and easy solution here? Thanks.