Lets take a look.

First, select any cell in the pivot table.

Next, snag the calculated field you want to work with from the name drop-down list.

you’ve got the option to now update the formula as you like.

To make an easy example, well modify this formula by adding 100 to the result.

hit the Modify button to update the formula and leave the dialog box open.

Click OK to update the formula and terminate the dialog box.

you’re able to now see that the formula has been updated.

Note that you cant undo changes made using the Calculated Field dialog box, so be careful.

We can follow the same process to change the calculated field back to the original formula.

You dont need to poke the modify button, you could just click OK after making changes.

The calculated field will be removed from the pivot table but it will remain in the field list.

Check the box again to add the field back to the pivot table.

You will need to update the field name again, if you changed it, and the number format.

Then smack the Delete button.

The calculated field will be permanently removed from the field list and from the pivot table.