I have a spreadsheet with the twelve months of the year and a dollar figure associated with each month. I wanted to highlight the highest and lowest value of a given row. You'll need to highlight all the cells you want to operate on, and select conditional formatting. In the conditional formatting section the rule you want to match is max(A1:Z1), but substitute the range of the text you're searching in. That will tell Open Office (or Excel) to match whatever is the highest out of the range you give it. Tell it to format that bright red or green and you're done!
Borrowed from SuperUser.