Selecting from MARC using a dummy plant

I have a table ZTAB1 which contains a list of plants and materials. I have an internal table gt_results which will have plants, materials and purchasing groups (EKGRP).

I want to put all the plants and materials in ZTAB1 into gt_results. For each plant/material I also want EKGRP which should be selected from MARC using the material from ZTAB1 and using a dummy plant 'dm01'. But the original plant should be passed to gt_results.

Can someone tell me the best way to do this?

Many thanks.