There are many ways to skin that cat, and yours is as good as any other. I definitely want to enter my rate of return and I know what rates of return I want my spreadsheet to assume (based on my AA and Rick Ferri's projected real returns for the next 30 years).
My spreadsheet takes as inputs: current age, retirement age, end of plan age (when I go poof), inflation, rate of return, current taxable assets, current deferred assets, pension value, my SS and my wife's SS with starting ages, SS reduction (I use 50% of what my statement projects) and all the additional savings while I'm working (taxable, IRA's, 401k, etc.). It also takes a table of 'special expenses' (adjusted for inflation) and the tax tables (adjusted by inflation +1%). I use conservative/pessimistic assumptions throughout. It knows to account for RMD and it then 'solves' for a starting after tax annual expenses (including special expenses) and inflates each year by the assumed inflation. If all goes according to plan I will die broke at 97. But again, many ways to approach this and there is no plan with a high probability of being correct 30-40 years out anyway, I know I'll need to be prepared to adjust for contingencies...
No one agrees with other people's opinions; they merely agree with their own opinions -- expressed by somebody else. Sydney Tremayne
Retired Jun 2011 at age 57
Target AA: 50% equity funds / 40% bonds / 10% cash
Target WR: Approx 2.5% Approx 20% SI (secure income, SS only)