you have to create a table with users list (USERID, USERNAME fields) in aggregated app which will be automatically filtered by section access. Then in the detail app, create an odag variable like :
SET USERNAME = ;
SET USERNAME = $(odso_USERNAME);
Let vUSERNAME = Replace($(USERNAME), 'CHR(39)', '');
This variable will contain your userID value (for example: john.doe) to use as a filter in where conditions or wherever you need it.