Item Fulfillment sorted by Sales Order

I Have created a suitlet where we display all items under a sales order in a sublist. When I select 2 items from 1 sales order I get 2 item Fulfillment record.
This is what we dont want. It should be like for 1 salesorder there should be 1 item fulfillment irrespective of the no. of items selected under it.
My code is:
else
{

iline = 0;
var line = request.getLineItemCount('custpage_markall');
for(i = 1; i <= line; i++)
{
var checkbxval = request.getLineItemValue('custpage_markall','custp age_itemful1', i);
if (checkbxval == 'T')
{
var item1 = request.getLineItemValue('custpage_markall','custp age_itemful2', i);
var salesorder1 = request.getLineItemValue('custpage_markall','custp age_itemful5', i);