I have a large workbook (14MB) that contains 3 months of 1 minute data in
three tabs that is cut and pasted from another spreadsheet that does the
calculations on the monthly data and another tab that calculates 1 hr
averages from the three monthly tabs. The workbook has been set to manual
calculation. When I add a simple line chart of the 1 hr average data (2 y
variables, date as text as the x variable) to the workbook, excel wants to do
"something" EVERY time I click the chart with a mouse. I look at Windows
Task Manager, and the excel process shows 25% usage (1 of the 4 CPU's maxes
out).

Thinking that the issue was the number of calculations occurring in the
workbook, I went thru a painstaking process of of converting all the
calculated data to values, eliminating all calculation in one version of the
spreadsheet. This did not resolve the problem.

Can anyone explain why this is happening, and what can be done to prevent
this from happening?