Hello,
One way to do this is to use a trigger.
Something like that:
Create Trigger UpdateData
On Table_1
After Insert, Update
As
Update Table_1 set Value = Quantity * 2;
Each time an update or insert will be performed, the trigger will be called, you can put what ever SQL you fancy in the trigger.
http://msdn.microsoft.com/en-us/library/ms189799.aspx[
^]
Valery.