You can do it if you make use of the Time-line X-axis in the Area Chart
type. By careful choice of numbers, you can create a rectangular area
that looks exactly like a conventional bar chart, but where the width of
each bar is under your control.

You can also make a stacked area graph look like a stacked bar chart in
the same way, and by eliminating the spaces between the stacked bars,
you can make a Matrix chart.

See this example of mine:

http://www.branta.demon.co.uk/excel/DCVarBar.xls