Sergey, should this offers further info, here's the structure of the source table:

CREATE TABLE `purrrdetails` (
`ID` int(11) NOT NULL AUTO_INCREMENT,
`RRHeaderID` int(11) NOT NULL COMMENT 'Taken fron bw.PurRR\nHeader.ID',
`InvItemID` int(11) NOT NULL COMMENT 'Taken fron bw.InvItems.ID\n',
`UnitID` int(11) DEFAULT NULL COMMENT 'Taken fron cw.Units.ID\n',
`PackingID` int(11) DEFAULT NULL COMMENT 'Taken fron cw.Units.ID\n',
`UnitCost` decimal(12,2) DEFAULT NULL,
`Qty` decimal(12,4) NOT NULL DEFAULT '1.0000',
PRIMARY KEY (`ID`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT='Receiving Report composition';

Thank you.

The quantities are entered from a Xojo app and they are stored in a mysql table.

You're generating reports from Xojo, right? Maybe (for the start) it will be simpler to populate the intermediate table in Xojo code.
Also, how do you get the quantities for each item? I'll try to create an example to do this task entirely in the Valentina Studio.

Uhmmm... I don't know if this is the right avenue to ask for help but I am not good in DB handling. I would be glad if you can point me to a sample stored proc that populates a temporary table from a field value of another table?

Hello Dale,

Looks like the only way to do it is to use a stored procedure and a temporary table:
1) Stored procedure fills the temporary table with records - one record for each label
2) The report is printed from this temporary table