To manually rename a chart object:

1. Hold the Ctrl key, and click on the chart to select it
2. Click in the Name box, to the left of the formula bar
3. Type a new name, or edit the existing name
4. Press the Enter key

LB wrote:
Excel assigns a name to each new chart object on a
worksheet as they are created (Chart 1, Chart 2, ...).
If a chart is deleted the next chart created is assigned
the next sequential number, so if the last chart built
was "Chart 7" and you delete it and add another chart, the
next chart is assigned "Chart 8." I would like to
rename "Chart 8" to "Chart 7." Is there any way to
accomplish this?

--
Debra Dalgleish
Excel FAQ, Tips & Book List
http://www.contextures.com/tiptech.html