Excel, under Functions, can calculate the Present Value of a future annuity (the projected monthly pension). But to determine the pension amount, I suggest you read the Plan Description to find the pension formula. You’ll need your current age, current monthly earnings, etc.

Or call the Human Resources Dept and ask them. Then use their estimated monthly pension to get the Present Value. Use a discount rate comparable to current market rates, or better yet, the discount rate used by the actuary in projecting pension cost for the company. See Footnotes to Financial Statements as a starting point.