Another research tree question

[Elowan]

Say that there are 5 levels in a specific tech. How would you restrict the upper 3 to a specific race or would you have to establish a new Category and then use race plus having researched the 1st tech (both levels) as prerequisites for the Last stage? http://forum.shrapnelgames.com/images/icons/confused.gif

[Gandalph]

In the components or facilities gained in the upper 3 levels, add a second tech requirement and make it racial.