highlight cells with values outside a specific range

I am truly an excel dummy and need excel to highlight certain cells according to the value in the cell. I'm pretty sure it can be done but don't have the slightest clue about how to do it.

Here's the scenario: I have a machine that saves certain data each time it performs its specific task. That data can then be exported in comma delimited format. Once excel has imported this data, I have a sheet with 12 columns X no less than 36 rows; may be more than 36, but never less. The values in each of the cells will be, typically between -.10 and .10. The values can be much more or much less. What I need is for excel to highlight cells with values in excess of .30 and less than -.30.

Once this is accomplished with 2 separate worksheets, I need to average the 2 worksheets, then highlight the cells with values in excess of .20 and less than -.20

Any assistance greatly appreciated.

Thanks ... dan