Data Services logic.

Hi, We are on DS 4.1. We have a requirement where we want to convert the value to C if any of the parent has the value as C. Source data is as given below.
 
LineNo  ParentLineNo Value
1                  0              G
2                  1              C
3                  2              C
4                  3              S
5                  4              S
6                  5              S
7                  6              S
8                  1              S
 
In the above example I need to convert the value for line number 4,5,6,7, to C from S as when we traverse through the hierarchy then we get value for one of the parent to C.
We want to keep S for 8 line number as its parent does not have value as C.
I did create loop to keep on doing this. It does what I mentioned but it executes 33 times. We need a better way to do this