Increasing Capacity Using RAID

I have a server currenty running with a mirrored RAID array. I want to increase the hard disk size and so am ready to buy 2 new drives of a larger size than is currently in the server.

My question is this. Can I put one of the larger drives into the server, get the RAID array to copy all the data to the larger drive and then put in the second larger drive (replacing the drive that the data was just copied from) to complete the mirror? I realize that when the different size drives are in together I will only be able to use the capacity of the smaller disk but once both larger drives are in is it easy to allow use of all the larger disks.