Use the Modify Variable dialog box to change the value,
  scope, and use of existing variables.

  Changes that you enter affect all the variables that
  you specify.

  You can specify variables by first selecting
  (highlighting) them in an active variable view window
  or by explicitly entering the names in the Variable
  field by specifying a variable name, a wildcard
  character, a wildcard character combined with a
  variable name, or a list of these separated by commas.