Did you find a solution to your issue described here?
If assistance is still needed, please supply a small - (5-10 rows per sheet) example data set and tell us what version of Tableau you are working with. My first thought is to utilize a union join between the three sheets but they would need to have some data element to identify the year on each row. Once we see the data and know what version of Tableau is in use, we can provide options that might work for you. A sample data set helps a bunch for the users of the community to jump in and assist.