Looking at your original post, I'm a little confused as to why you need to edit a cell.
If you use Spreadsheet::ParseExcel::SaveParser you load in your existing spreadsheet
then create your new worksheet:
$oBook->AddWorksheet('February');
To this new blank worksheet first add the cells from the prior month's worksheet that are the same in the new month's worksheet for example:
my $oOld_Sheet = $oBook->{Worksheet}[0];
for (my $row = 0; $row <= 4; $row++) {
my $oCell = $oOld_Sheet->{Cells}[$row][0];
if (defined $oCell->{Val}) {
$oBook->AddCell(1, $row, 0, $oCell->{Val}, $oCell);
}
}
Adding the sales for the new month to the new sheet using the AddCell method as well.
Finally save the workbook under a new name using the SaveAs method.
If you really need to edit a cell then Win32::OLE as InfiniteSilence and davidrw mentioned is probably what you will have to use, also if the worksheet you are adding contains formulas.