Here's my 1st attempt at a solution. You didn't say what type of chart
you are using, or any other details, but this worked for me, in one
form or another for a scatter plot, line graph, and a column chart.

1) Assume dates are in consecutive order in column A, sales figures for
each date in column B.
2) In column C, in rows corresponding to event dates (include dates in
between start and end), enter the minimum Y value in the chart. Other
rows left blank
3) Add column C as a series to the chart, formatted as a colored line
without markers.

This gives colored lines that show the dates over which the events
occured.

As an extension, you could use more columns and additional series to
indicate different event types -- say a red line for the "promotional"
event, a blue line for the "transition" event, and a purple line for
the "marketing" event.

If it was hard to see on the X axis, set the value to something a
little above the minimum Y value, or something near the maximum Y value
to put the event lines near the top of the chart.

Was that worthy of an honorable mention:)?


--
MrShorty
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