This is great! I would definitely use it, but the one little thing I don't like is when the formula contains cell references (eg. 'D1') the references appear in the graphic and spoil it a bit. This is not really your fault though.

Fortunately if you name a cell in Excel (using the Name Box just to the left of the formula bar) and then refer to the cell using name instead of reference, and that looks a lot better (more like a proper equation). But I wonder how many Excel users even know about the Name Box?

What could be nice is if your macro could check all cell references in the formula to see if the cells had already been named - and then update the formula to use the names instead - else prompt the user for a name (optional) for each reference which would then also be saved (possibly via the Name Box).