locate-file

• (send a-mred:frame-group locate-file name) -> a mred:frame% object
      name : string

  Accepts a name of a file, and finds that file in the group. If it is in the group, return the frame, otherwise return #f

  This considers the editing-this-file? in mred:media-edit% or the editing-this-file? in mred:pasteboard% instance variables.