Excel 2007 Quirks While Conditionally Formatting An Entire Column
When conditionally formatting an entire column, you create a rule that tests the value of a cell in some row. Then you establish the format to be applied to some cell (typically in the same row), if the rule evaluates to true.
Then you copy/paste or fill (most likely in the down direction) the formatted cell to cells in adjacent rows. For example, you have a three column table: the first column is the student name, the second column is the score they received on a test (from 0 to 100) and the third column is some formula (not important for this discussion) that converts the numerical score in the second column to a letter grade. You want the letter grade in the third column to be red if the numerical score in the second column is below 70. You select cell C1 (the first row that contains a letter grade) and add the following rule: B1 < 70. Simple. Now you select C1 (again) and drag it down to C30 (the last student in your class occupies row 30) and hit Control-D to drag the conditional formatting down into column C of rows 2 through 30. Note that you get the desired results.
Here's the odd thing. Select cell C15. Look at the rule that is in effect for the selected cell. Excel displays the rule as "B1 < 10" and you are expecting it to say "B15 < 10". When deciding what formatting to apply to C15, Excel is looking at B15, even though Excel (stupidly, in my opinion) displays B1 in the rule. Now, here's why it took me a while to figure this out. If there is a mistake in the rule, one that prevents the rule from being evaluated, then the conditional formatting is not applied, leading you (well, me anyway) to thinking that the rule was evaluated, only to false, further convincing me (incorrectly, as it turns out) that Excel was looking at B1 (after all, that is what Excel displays when presenting me with the Conditional Formatting dialog boxes).
So, in conclusion, Excel does look at the cell you would expect it to look at when evaluating a rule to be applied to a column, even though when displaying the rule, the wrong cell is identified.