There are a couple of commercial sparkline chart programs (Bissantz Sparkline Tools and BonaVista Systems MicroCharts) which essentially use special fonts to draw small charts in the cells. They’re COM add-ins created with .Net, not VBA, but they have special code that changes colors. They use the COM/.Net equivalent of UDFs that return whatever text is needed in the special font to create the chart.

also WTS fonts (for blind people) do have some kind of bar graph possibilities as they have blocks of different heights (one third, two thirds and three thirds) so using vba and colors it might be possible to replace sparklines with simple text.
Best option would still be to build a font dedicated to in cell charts to have something with a very light footprint and minimal knowledge of formulas / vba (vba to add colors)

Unfair to the Juice guys? I don’t think so. I wrote comment #6 below Chris’ first post (Lightweight data exploration in Excel):

Nice demonstration of “less is more” and “keep it simple stupid”. This is one of those elegantly simple approaches that everyone always forgets.

My comments following Chris’ second post were not particularly germaine to the REPT approach, I was mostly showing what could be done with some simple VBA and colored rectangles (and a client without regard to the appropriate use of colors).

The pipe character makes an elegant chart, and in fact any character you like from any font makes a reasonable bar chart. J Walk liked the blocky Wingdings character because it gave the bar a bold appearance. The nice thing with using monospaced fonts is that you can use different characters for different markers (or spaces) and things will readily line up.

So what was new to me? A tiny little twist with a big impact, the introduction of narrow characters from proportional fonts. Previous explications of the “in-sheet chart” idea, including I believe John Walkenbach’s, had used monospaced fonts with every character no less wide than the letter M or W, which was never all that satisfactory to me. I think I said at the time on the Juice blog that the simple addition of Unicode characters made such a difference to the precision and look of the bars that it was like a whole new thing even to someone like me who had the basic gist fifteen years ago.