Very neat.

Thought I'd have a crack at doing something similar in Rebol. Here's my attempt:

  Rebol []
 
  ; Here's the beef!...  the spreadsheet object
  spreadsheet: context [
      update: func [block /local b] [
          b: compose/deep block
          bind b self   ; so action happens in object context
          do b
      ]
  ]
 
  ; make sheet with following cells
  ss: make spreadsheet [
      a1: 5
      a2: does [a1 * 6]
      a3: does [a2 * 7]
  ]
 
  ; simple usage example
  print ss/a3  ; => 210
  ss/a1: 6   
  print ss/a3  ; => 252
 
  ; use /update method to keep it within the objects context (needed for DOES)
  ss/update [a3: does [a1 + a2]]
  print ss/a3  ; => 42
 
  ; and compose in variables from current context, see (a1) 
  a1: 1000
  ss/update [a3: does [a1 + (a1)]]
  print ss/a3 ; => 1006

You could probably do something very similar in other prototype based object languages.