I must admit, though, that I was a little disappointed with how the above works... I had hoped besides pushing values into "foreign" cells, that it would be possible to affect other environmental properties via the subroutine called by the HYPERLINK function when evaluated by the Evaluate function, but unfortunately, it does not appear so... all attempts to do things like change the "foreign" cell's interior fill color or font color failed (no errors were raised, the code lines attempt to do this were simply ignored). Oh well, what it can do is still pretty neat, I just wished it could have been neater.
Rick,

This worked for me

Code:
Sub TooCool(InCell As Range, PushTo As Range)
  PushTo.Value = "The square of " & InCell.Value & " (in " & _
                 InCell.Address(0, 0) & ") is " & InCell.Value ^ 2 & "."
    PushTo.Interior.Color = vbYellow
    PushTo.Font.Color = vbRed
End Sub

Function DoCool(Rng As Range) As String
  If Rng.Value < 0 Then
    DoCool = "Number in " & Rng.Address(0, 0) & " is less than zero."
  Else
    DoCool = "Number in " & Rng.Address(0, 0) & " is greater than, or equal to, zero."
  End If
  Evaluate "HYPERLINK(TooCool(" & Rng.Address & ",J3))"
End Function
M.