Combine multiple columns into one, automatically?

[Lon]

I'm trying to create a chart that will automatically combine into one column
what are now several columns when displayed in an ordinary column chart.

The columns I want to combine all have the same value on the Y-axis, but are
shown (in an ordinary chart) as separate columns because they have different
values along the X-axis.

Is there any way to create a chart that will automatically add together the
X-axis values and then display the results in a single column?

Or, is this not really a "charting" problem, but instead a problem that
requires me to recalculate my data before the chart is drawn? I've
recalculated it "by hand" and then created the kind of chart I'm looking
for. But I'm looking for a way to do it automatically.