How to add new fields to standard reports

hi friends,
             im into ABAP and working across all modules..the basic thing is users and functional people are not satisfied with the standard reports..they need some logic change or to add some more fieldsinb the standard reports.For logic change we have to copy the standard to zprogram and can do or create a new program itself..but in many cases they ask for extra to achive it ..
for example my requirement now is adding vendor name field to the report FAGGL03 ....i found a badi and have make changes to it the vendor name will be coming in sgtxt over writing the text ...but they need text what shall i do???
append structure vendor name field in faglposx table ....???how to find out the final internal table from where the output is coming ????
?when we check the standard rewport codes...there are lot of include statements perform statements etc to find out the final structure or internal table which has the output values..???


it would be better if u giv full name of the report
if ur displaying the data in alv then search for the
word REUSE_ALV_LIST_DISPLAY REUSE_ALV_GRID_DISPLAY from which u can get the final table name
then check the data that is comming into
try using implicit enhancement or any other exit in the declaration and declare a new structure with the field and append it to the field catalog
if ur displaying the data using write statement
then create a zprogram and add a write statement
fi ur unable to find here the final table then after displayign the report start the debugging and double click on any row to find out more easily