Ztable Last modiefied by and Last modified on not updating
I have a problem updating two fields "modified by" and "modififed on" of z table. I am using a event 18 through the view v_tvimf and SM30 to move sy-datum and sy-uname to the above said fields. It is updating the fields at one instance of the run but finally it is been over written by the buffer ( I suppose ) with old values of "created by" and "created at".
I would really appreciate if some one can help me out in this issue and thanks in advance.