PHPExcel row/field custom metadata?

[latinbeat]

I use PHPExcel to export data from mysql and \[code\]$workbook->getProperties()->setCustomProperty()\[/code\] to store table name.But i'd also like to store an *primary_key* field for importing without having visible column for it.And it should stick to the row so editors can delete rows.PHPExcel is lacking of documentation so i didn't find anything at the moment.Is it even possible? Haven't digged into \[code\]OfficeOpenXML\[/code\] docs yet - looking for existing solution.Cheers!