If you are able to calculated the values needed to populate the fields you want to create then you may be able to add them to the P&L. If you need those fields to be present in the database, then no you cannot. Tableau is a reader of data and will not write those values back to the database. But as I first stated, if you are able to calculate the values from the data that you already have, then it can be presented in a new column. You will have to keep in mind where things are being aggregated or you may have some odd numbers. If you could share your file here, remove the name of the company, then there are plenty of people here that can help.