Calling-Station-Id and Called-Station-Id values

Hi, How can I make Calling-Station-Id and Called-Station-Id to be see in accounting if one of them is empty in detail log file. What I mean if one of the field (Calling-Station-Id or Called-Station-Id ) doesn't supplied by NAS I want it to be seen like : Calling-Station-Id = "xxxx" Called-Station-Id = "" or Calling-Station-Id = "" Called-Station-Id = "yyyy" Right now if one of the attribute is empty it is now shown in detail log file like: User-Name = "10.241.1.14" Called-Station-Id = "xxxxx" Acct-Status-Type = Stop or User-Name = "10.241.1.14" Calling-Station-Id = "yyyyyyyyy" Acct-Status-Type = Stop Regards.