Hi Ram,
Redifine the Get_I method of the attribute and use a code similar to below. In the below code the Last line of table is set to Editable.
DATA:
lv_curr TYPE sytabix,
lv_last TYPE sytabix.
rv_disabled = true.
lv_last = iterator->size( ).
lv_curr = iterator->get_current_index( ).
IF lv_last = lv_curr.
rv_disabled = false.
ENDIF.
Hope it helps you 
Regards,
Pratheek