Signet7 - I started this game just over a year ago and after a few weeks of playing I went down the same path that you're heading down now...building my own shot calculation spreadsheet. I'm also an engineer and love spreadsheets so I did a lot of research on the forums, downloaded a few shot calculators that other people had built and used them as a basis for my own shot calculation spreadsheet.
After tweaking that spreadsheet for my own equipment I found it worked very well. At lower levels, when I used the spreadsheet, it was pretty rare that I wasn't within 10 feet of the pin on my approach shots. The accuracy of that spreadsheet seemed to get worse once I hit higher levels and was able to buy more advanced equipment and balls. Somewhere when my level hit the mid 80's I stopped using the spreadsheet entirely because it became increasingly difficult to tune the spreadsheet to my new equipment. I knew my equipment would keep changing a lot until I hit level 100 so I stopped using my spreadsheet and planned to go back to it after I "finalized" my equipment.
I ended up playing without a spreadsheet for about 7 months. When I hit level 100 I felt that my equipment was pretty solid and wouldn't be changing very much so I tried going back to the spreadsheet. I spent about 2 weeks trying to tune my spreadsheet to my new equipment. What I found is that I could tune it pretty well for a few courses, but it didn't work well for all courses like it used to for me when I was a lower level player. I'm not sure if WGT throws some additional penalties / calculations as you level up and tier up, or if the game variables are just more complicated with the higher level of spin / precision / forgiveness of the equipment and the higher spin rates on the balls. After trying to tune the spreadsheet for 2 weeks I quit using it again.
I will say I enjoy playing without a spreadsheet a lot more than I do with it. Once you get good course experience and understand how the different holes and greens play with your equipment, you'll find you can play this game very well by feel and a few simple calculations that you can do in your head.
If you still intend to go down the spreadsheet route add me as a friend and send me a message. I'd be happy to send you my spreadsheet. If nothing else you can look at some of the formulas / variables and use whatever makes sense.
I think for any shot calculation spreadsheet to be effective you'd have to find a way to account for all the equipment and ball stats and allow for individual course variables to be input that would help account for their differences in wind effect, fairway roll and green speed.