Why does spreadsheet bog down when data in some cells?
 

If I have any data in certain cells in a particular worksheet, the program
bogs down. As I click from cell to cell it takes up to 15 sec for the cell to
be highlighted, or if I try to click on "File" or any other pull-down menu,
it also takes up to 15 sec to come down. Once it does, it moves normally
until I return to the worksheet. If there is no data in the cell, I have no
problem. If the data in the cell is currently off my screen, I have no
problem. It is only an issue when there is data present and I can see it on
the screen.

I'm stumped. Can anyone help?