How can I set the work for a task to be a percentage of another task ?
Example:

Task 1.1 = Software Development, work = 80 hours
Task 1.2 = Software Testing, work = 20% of Software Development work

I can manually calculate 20% of 80 hours and enter it for task 1.2, but when the work assigned to task 1.1 changes later due to increased requirements, I'd like task 1.2's work to automatically update. (There are many tasks like 1.2, and a manual approach results in the possibility of missing some during replanning updates).

ps: I'm using Project 2003.

Thanks.