Inventory detail subrecord

Hi All
While fulfilling the SO  i am setting the serial numbers of the items in the inventory subrecord and imediately after setting the serial numbers i need to fetch those values for performing the validations. But problem is that i could get only 1st line -serial number and
remaining lines are not fetched
Even if i select the 2nd line directly still it's showing the 1st line serial number itself
var seril = new Array();
var cnt = invDetailSubrecord.getLineItemCount('inventoryassignment');
for(var j=1;j<=cnt && cnt != -1;j++){
invDetailSubrecord.selectLineItem('inventoryassignment', j);
seril[a] =  invDetailSubrecord.getCurrentLineItemValue('inventoryassignment','issueinventorynumber');
a++;