I received the following error message when I tried the percentage change formula:
"DataSource.Error: An error happened while reading data from the provider: 'The provider could not determine the Double value. For example, the row was just created, the default for the Double column was not available, and the consumer had not yet set a new Double value.'
Thanks for being patient with me. I am very new to this whole power query thing and trying to learn the hard way 