ABAP QUERY - SQ02 addition of logic in infoset (END-OF-SELECTION)

I guys I have read this discussion: http://scn.sap.com/message/8193608#8193608

but solve partially my problem.

In particular I need special logic to interpret the single field from field symbol, for example:

loop at <goo> assigne <goo_wa>.

tot_qty = tot_qty + <goo_wa>vbap-zmeng.

endloop.

I would like to add new row, with my logic into stracture of query %G00.

thanks for any idea Omar