Hi:
Look at pages 2,3, and 4 in this paper. The general outline of how to add to or alter code is here. Basically, EG will give you places where it is appropriate for you to enter your own code. If you wanted to change some -statement- within the code that EG has built, however, you'd have to go back and reselect or change your choices in the various task panes (for example you want to change AGE to HEIGHT -- but EG has already put AGE in the code that you see in the Preview Code window -- to get HEIGHT, you'd have to reopen the task and select HEIGHT instead of AGE.)
Anyway, the directions in this paper are very good:
http://www2.sas.com/proceedings/sugi30/019-30.pdf
cynthia