Descent winds should be entered latest enroute some time before you start your actual descent. On our OFPs we have descend wind forecasts for FL310, FL200 and FL100, just right to fill the three forecast lines in the Descent Forecast Page.
On route sectors with less than 100NM remaining to the next waypoint putting him on top and execute again will indeed recalculate your VNAV profile using spot wind and interpolations between either zero zero wind at EoD or your entered descent winds.
Anyway, it is much easier to correct for a wrong descent wind on the classic than it is on the NG, the difference is quite big, even more so between a small classic (500) and a big NG (800/900).