Need coloured background columns in chart for easy pattern recognition

I am making a chart to show the daily natural gas usage for an apartment building.

The x axis grid lines are the days of the month in the format dd/mmm/yyyy.

There are 2 lines across the x axis.

One is for the daily temperatures from -25 to 0 degrees Celsius in 6 hour intervals.

The other line is for the cubic meters of natural gas used over an 8 to 12 hour period during the day.

The y axis range is from -25 to +55 which is OK for my 2 horizontal lines since both horizontal lines upper and lower limits fall within those parameters.

The plot area is plain white with black gridlines. I want that simple. The 2 horizontal lines are red and green.

On Saturday and Sunday the natural gas goes up to almost double the Monday to Friday daily amounts used.

Therefore I would like to highlight these 2 days (Saturday and Sunday) where the line slopes up and then down by having a pastel colour in the 6th and 7th white plot area columns so it is easy to recognize the weekend on the chart.

I have EXCEL 2003 but I will upgrade if I have to to get the desired effect because I might need this chart for a presentation and I want the pattern of increased weekend use very easy to see.

Thanks in advance

Here is a chart showing the basic layout. Although there are fluctuations in the gas usage line there are other factors occurring in the building that cause the erratic daily gas usage that are not related to temperature alone.

I hope this chart will be sufficient to get some assistance.

Danny, from Ontario

Andy,

Is there a way to make the y axis grid lines go through the background colours?

Also, I opened the file with EXCEL 2010 on my laptop and the background gray colours don't fill the columns only and completely. They seem to be offset and shifted to the right taking up some of the adjoining column.

A side note:
I use Firefox and I couldn't download your file until I had the cookies turned on.

Danny from Ontario