If I understand you correctly, you want to get records from the JEST only if the records exist in the VBAP?
If you are using the SAP Connector maybe you could try left join the tables?. I can't test it now with the VBAP tables but below is the example syntax. As long as the tables are "transparent" the join should work.
SELECT MARA~MATNR, MAKT~MAKTX FROM MARA left join MAKT on (MARA~MATNR = MAKT~MATNR);
Please let us know how did it go.