I developed my own spreadsheet.
Excel Handicap.xlsx
It will take some explaining:
There are 2 columns of numbers on the left, the first column is the number of games in table (1-20), the second column is the order that the games are played, #1 being the most recent game.
When you add a new game you first must sort the table. Select the cells from C5 down and over to J24 and sort from smallest to largest in column C. Then you COPY from cells D5 down to J23, and paste it into cell D6. The top 2 rows should look the same, so you add your new game into the top row, over typing the date, the course, Par, Score, Rating, & Slope. This will show you a new "differential" for that game.
Now you need to sort to get the lowes 'differential' again select all the cells from C5 down to J24, and sort from the lowest to the highest in column J.
If you never moved any of the formulas your handicap should show at the right, in this case as "27.896" and rounded off above to 28.
If you have questions, be sure to ask, as I may not be as clear as I should be. This spread sheet I developed myself from the information on line, as how to calculate handicaps.