You can never have exact calculation for something you want to do in the future. When the time comes to do the job, you have to find a contractor to provide a quote. Everything in the capital works plan is a guess of what the work will cost (adjusted for inflation).
kaindub has the right idea. The capital works plan is simply a list of works you hope to complete in the next ten years. Beside each work, you guess how much it will cost. Since you won’t be doing everything in the next twelve months, you would assign some jobs for 2025, some for 2026, some for 2027 etc. The cost for jobs beyond 2025 have to be adjusted for inflation. Again, you have to guess the inflation rate.
I have already set up such a spreadsheet. next to each piece of work, I write the number 1, 2, 3 etc to show how many years into the future we want to do that work. That number helps me to adjust my cost for inflation one, two or three years away. Then I set up a second sheet to take a total of all the work I plan for each year. That would be a list of years 2025-2034 with how much we expect to spend.
I can adjust the estimated cost and the year I want to do the work. The capital works plan worksheet recalculates itself.
If you really want more info, I can explain the cell formulae in the spreadsheet.