Weekly bar chart needed for percentage results

Hi,

I've attached my current project which contains 2 worksheets. First one being the percentage of sales made using a store card over each week day.

What I am looking to do is on sheet 2 make a horizontal bar chart with the days of the week left/vertical and percentage bottom. But also to have a drop down box where I can select the week relative to sheet 1 to display the results in the chart.

I can make bar charts but can't work out how to make the chart update via using a drop down box.

Any help appreciated thanks.