" The Excel buffer already exist identification field and value Row No =2 Column No = 1" error why and how solve

Hi guys i have problem i grouping report to item ledger entry table data item as following :

item no        quantity    cost amount(actual)

ax                      5                    3000

az                      2                   4000

grouping by item no until now is successfully.

I try to print to excel sheet  using excel buffer table so that i write following code :

item ledger entry -on after get record trigger
IF PrintToExcel THEN
  MakeExcelDataBody;

CreateExcelBook() function

ExcelBuf.CreateBook;
ExcelBuf.CreateSheet(Text002,Text001,COMPANYNAME,USERID);
ExcelBuf.GiveUserControl;
ERROR('');

MakeExcelInfo() function

ExcelBuf.SetUseInfoSheed;
ExcelBuf.AddInfoColumn(FORMAT(Text005),FALSE,'',TRUE,FALSE,FALSE,'');
ExcelBuf.AddInfoColumn(COMPANYNAME,FALSE,'',FALSE,FALSE,FALSE,'');
ExcelBuf.NewRow;
ExcelBuf.AddInfoColumn(FORMAT(Text007),FALSE,'',TRUE,FALSE,FALSE,'');
ExcelBuf.AddInfoColumn(FORMAT(Text001),FALSE,'',FALSE,FALSE,FALSE,'');
ExcelBuf.NewRow;
ExcelBuf.AddInfoColumn(FORMAT(Text006),FALSE,'',TRUE,FALSE,FALSE,'');
ExcelBuf.AddInfoColumn(REPORT::"TotalQuantity-Cost",FALSE,'',FALSE,FALSE,FALSE,'');
ExcelBuf.NewRow;
ExcelBuf.AddInfoColumn(FORMAT(Text008),FALSE,'',TRUE,FALSE,FALSE,'');
ExcelBuf.AddInfoColumn(USERID,FALSE,'',FALSE,FALSE,FALSE,'');
ExcelBuf.NewRow;
ExcelBuf.AddInfoColumn(FORMAT(Text009),FALSE,'',TRUE,FALSE,FALSE,'');
ExcelBuf.AddInfoColumn(TODAY,FALSE,'',FALSE,FALSE,FALSE,'');
ExcelBuf.NewRow;

ExcelBuf.AddInfoColumn("Item Ledger Entry".GETFILTER("Item No."),FALSE,'',FALSE,FALSE,FALSE,'');
ExcelBuf.NewRow;
ExcelBuf.ClearNewRow;
MakeExcelDataHeader;

MakeExcelDataHeader() function

ExcelBuf.AddColumn("Item Ledger Entry".FIELDCAPTION("Item No."),FALSE,'',TRUE,FALSE,TRUE,'');
ExcelBuf.AddColumn("Item Ledger Entry".FIELDCAPTION(Quantity),FALSE,'',TRUE,FALSE,TRUE,'');
ExcelBuf.AddColumn("Item Ledger Entry".FIELDCAPTION("Cost Amount (Actual)"),FALSE,'',TRUE,FALSE,TRUE,'');

MakeExcelBody()

ExcelBuf.NewRow;
ExcelBuf.AddColumn("Item Ledger Entry"."Item No.",FALSE,'',FALSE,FALSE,FALSE,'@');
ExcelBuf.AddColumn("Item Ledger Entry".Quantity,FALSE,'',FALSE,FALSE,FALSE,'');
ExcelBuf.AddColumn("Item Ledger Entry"."Cost Amount (Actual)",FALSE,'',FALSE,FALSE,FALSE,'');

Report - onprereport()

itemFilter := "Item Ledger Entry".GETFILTERS;
PeriodText := "Item Ledger Entry".GETFILTER("Posting Date");

IF PrintToExcel THEN
  MakeExcelInfo;

Report-onpostreport()
IF PrintToExcel THEN
  CreateExcelbook;

Then when i run report i found error tell me as following :

" The Excel buffer already exist  identification field and value Row No =2 Column No = 1"

How i solve this problem.

thanks