merging cells

Hi, I'm creating a master spreadsheet which is the compilation of 5 people's comments on the same initial spreadsheet. I'm designing my master spreadsheet to allow for easy viewing of everyone's comments on some, but not all cells. For this reason, I would like to merge many cells--all those cells in which no one made comments--and on occasion, I would like to leave 4-5 rows of data. Is there an easy way to merge many clusters of cells without having to do each cluster separately?
Thanks for any suggestions . . .