Option Explicit
sub Testme()

Dim cCtr as long
dim myCell as range
dim myCol as range
dim myArea as range
dim myRng as range

dim myAddr as string
dim wks as worksheet

myaddr = "a5:I10"
cctr = 0
for each wks in activeworkbook.worksheets
 Set myrng = wks.range(myaddr)
 for each myarea in myrng.areas
   for each myCol in myarea.columns
      for each mycell in mycol.cells
         cctr = cctr + 1
         if mycell.comment is nothing then
            'do nothing
         else
            mycell.comment.delete
         end if
         mycell.addcomment text:=format(cctr,"0000")
      next mycell
   next mycol
 next myarea
next wks
       
End sub      

I have no idea what you really want in your comments, so I just plopped in a
sequence of numbers--while deleting the existing comments!