I'm able to do data bar conditional formatting in Excel 2010, but I can't figure out how to switch the bar axis to make it vertical. Is there any way around this? Can I simulate a vertical histogram with conditional formatting?
Data bars in conditional formatting are Left-Right or Right-Left only. There's no Up-Down or Down-Up option available.
The only way to get a vertical data bar-type look would be to use a formula and change the Fill settings to a gradient, but you don't get enough control over the gradient to differentiate the different values.
Another option is to spark lines. There's a nice example of something that might do what you want here: http://blogs.office.com/b/microsoft-excel/archive/2009/07/22/formatting-sparklines.aspx
You can't change the conditional formatting in Excel to create a column chart instead of a bar chart. This conditional formatting isn't creating a true Chart object in Excel, so you don't have the same flexibility in modifying its appearance.
Instead, you can create a
EDIT: Based upon your notes, and borrowing from @Rhys Gibson, here's a solution using sparklines (which are available in Excel 2010, or add-ins pre-Excel 2010). I've included both the conditional formating bar charts (nearly impossible to make sense of), and their sparkline equivalents.
EDIT: One other point that may seem relatively minor, a Histogram is not a Column (or Bar) chart. They are distinctly (if subtly) different chart types and the terminology shouldn't be interchanged. For a great description of the difference, check out Naomi Robbins' A Histogram is not a Bar Chart