Posting labels to printed invoice

[kjuntura]

Hello experts,

 

I have modified invoice.php for my need, so that invoice prints also posting labels which I can tape over parcel.

Any idea how to choose which kind of label printed to invoice dependig which shipping method has customer paid. I have now two Economy and Priority but if many items in order then label goes to another paper sheet, cause I have both bottom of invoice.

 

http://eopen.fi/pub/eopenlasku.jpg