Enhancing standard WD component controller exposed as interface controller

Hi Experts,

I have enhanced the standard WDC DPR_DET_DATA_PROJECT_O(exposed as interface controller) and added four cutom UI elements using Zfields from my ztable. Now I need to update the zfield values in my ztable after the user performs save action. I came to know that method ON_SAVE_REQUEST of WDC -  DPR_PROJECT_STRUCTURE is doing the save operation.

I tried to expose my node as Interface node in DPR_DET_DATA_PROJECT_O to get the values in DPR_PROJECT_STRUCTURE, but it is not possible according to SAP. So how can I proceed further to read my context values from component  DPR_DET_DATA_PROJECT_O into DPR_PROJECT_STRUCTURE.

Also have read that I can use ABAP class with singleton pattern, but am unaware of it. So is there any other way to read my context values into component DPR_PROJECT_STRUCTURE.

Please suggest me and give your valuable ideas.

Thanks,

Ramakrishnan M