Did you know you can name a range in Excel, and you can refer to it later. You can store these numbers 1 through 9 in excel.
Select the 9 cells, then on the top left corner change it's column name range to a new name : matrix. Then click enter.
In a new cell, you can type =sum( which is the sum function, instead of drag and select the range, just type the name you give to the range : matrix. Close the parenthesis. =sum(matrix)