Hi Susan
Which datasource you are using at present. Normally 0PUR_C01 gets loaded from 2LIS_02_ITM and 2LIS_02_SCL. The keyfigure that you have mentioned will come from 2LIS_02_SCL with the code that you have written.
The code that you have written should work. Please check if the code is in the transformation from 2LIS_02_SCL.
Share the details on why do you think the solution didn't work.
Regards
Karthik