Change validity end date on activity type

Is there a way to change the validity end date of an activity typre. Currently it is 9999 we would like to change it to 2011.

We would like to use a particular activity to cost current standards but dont want to use it for planned estimates that we will create for 2011. I am assuming if the validity ends in 2011 it will resolve the problem. I know we could create alternate routings and different production version but I am trying to avoid that and see if we can find a short cut.

Your help in this regard will be much appreciated