The tricky part is to get the formula right in the calculated column. I have already published step by step examples to help users get started. But as soon as users’ needs slightly differ from these examples it becomes difficult for occasional site designers to get it right.
In an attempt to make the method more accessible, I have built a Formula Generator. Fill out the form with your choice list and the associated colors, select one pattern (Background/Font color/Traffic light), and the Formula Generator will build the formula for you. Hopefully this will allow more users to benefit from the HTML Calculated Column.
I plan to build other formula generators in the future to accomodate other needs (progress bars, etc.). Spread the word!
Update [April 23rd, 2009] Based on readers’ feedback, I have added a formula generator for numeric values.