Pro Data Sets and the Fill Method

Using the code below, could someone tell me 1.) if it's possible and 2.) how to do it.

What I am trying to do is set the batch-size on a pro data set fill to 1000 records....(total records is ~500K)

Then <do something> with those records and then retrieve the next 1000.

I am getting the first 1000, but in the next interation, it just starts from the beginning.

Thanks, in advance for any and all help....

define Variable cWhereClause as char no-undo.
define variable icnt as inte no-undo.
define variable hTable as handle no-undo.

DEFINE TEMP-TABLE ttCorpa        NO-UNDO LIKE corpa.
DEFINE TEMP-TABLE ttCorpaIMA     NO-UNDO LIKE corpaima.

DEFINE DATA-SOURCE dsCorpa       FOR corpa.
DEFINE DATA-SOURCE dsCorpaIMA    FOR corpaima.

DEFINE DATASET OneTIS_Corpa FOR ttCorpa,ttCorpaIMA
  DATA-RELATION drCorpaIMA  FOR ttCorpa,ttCorpaIMA
RELATION-FIELDS(corpano,corpano)  NESTED.

BUFFER ttCorpa:HANDLE:ATTACH-DATA-SOURCE (DATA-SOURCE dsCorpa:HANDLE).
BUFFER ttCorpaIMA:HANDLE:ATTACH-DATA-SOURCE  (DATA-SOURCE dsCorpaIMA:HANDLE).

ASSIGN hTable = BUFFER ttCorpa:HANDLE.

assign hTable:BATCH-SIZE = 1000.

DATASET OneTIS_Corpa:EMPTY-DATASET().

ASSIGN cWhereClause = SUBSTITUTE("WHERE corpa.type1 = '&1'", 'CDO').

dataset OneTIS_corpa:FILL().
do while hTable:Last-batch = FALSE:
    assign icnt = 0.

    for each ttCorpa:
        icnt = icnt + 1.
        disp icnt ttCorpa.corpano .
    end.
    message icnt view-as alert-box.

    empty temp-table ttCorpa.
    dataset OneTis_Corpa:FILL().

END.