Logic for Cumulative fields of Extractor "3EC_CS_1A"

Hi Experts,

I'm creating Generic extractor which will replicate the functionality of Extractor '3EC_CS_1A',but having a hard time in finding logic to populate year till date(cumulative) key figures,I believe they are not coming from Table(ECMCT or ECMCA) but are getting populated by Extractors logic.

Please help me with logic to populate below mentioned fields,

YTD_LC

YTD_GC

YTD_TC

YTD_QTY

Regards,

Ajit Mishra.