Hey, I would be glad to help you out on this. I can send you a W&B Excel spreadsheet I use for my 1977 M20C Ranger. It should be pretty close to what you have. You should take the time to modify the weights according to your offical W&B sheet. If you need to adjust it, you will need your manual. Adjustments to the envelope are done by modifying the envelope box on the right hand side of the spreadsheet in the calculations area where it is hidden normally, column AA. These value control the settings for the calculations on the left which control the plotting of the graph. To adjust these, just look at the Owner Manual for the envelope. The corners of the envelope have two points, one from the bottom and one from the side. You just set the values by matching them up. Let me know if you need help adjusting it.
Once you have the spreadsheet adjusted, save it and never touch the right side again. When ever you need to perform a W&B for a flight, open up the spreadsheet and put the values in on the left side where it is a dark shaded grey then look at the results.
Send me an email to junkmail@faheys.org if you want a copy.
**** WARNING **** Do not use this spreadsheet without customizing it for your airplane and verifying the results.