Ronaldo,
make an SQL trace on you FOR ALL ENTRIES, and in the menu Summarize the entries. You will see the number of access of this statement.
second point, your
loop
read binary
it's good, but you cand do better
loop ...
read from index
if key VBAK > key VBFA
index = index + 1
if key VBAK = key VBFA
action
exit
if key VBAK < key VBFA
exit.
endif.
....
(I wrote really quickly before my breakfast 
)
Fred