http://www.primetab.com/flying/MyNavLog.xls

The sheet marked W&B has what you need. The sheet is for a Piper Warrior, but
you can adjust it for the Cessna numbers. You will need to unprotect the sheet
before making changes, Tools/Protection/Unprotect Sheet. Input the Cessna
numbers for Basic Empty Weight, all the Arms, Unused gallons, and GPH.
Everything else is calculated. Adjust the chart.