It would not need to be particularly elegant. If the program-spreadsheet exports the right data, it can be rendered or GUI-ed separately - even by a program that watches for export file changes. Even by a spreadsheet viewer for the people who insist.
A notebook lets you use various libraries or outside programs to do the rendering.
If have also done this with graphical objects (think postscript). The program is on one side and generates and composes primitives into useful blocks and arrangements. A - for example - postscript viewer is on the side, watches for updates and re-renders the thing. You now have graphics as programming, with synchronous-enough rendering.
But re:parent comment, I'm not sure I understand how you could handle the visualization independently