3UP LAbels Revisited

I'm in need of converting our lagacy RPG (AS400) label program from a
tractor fed 3 up/across label to a laser cut sheet (Avery 5260).

Each label down the sheet creeps further up the label. By the time the
end of the sheet is reached, the first print line is either on the
margin or the previous label. 

Have tried several different approaches but all attempts seem to yield
disasterous results or the "creeping" affect.

Can someone assist ???

 

Thanks in advance, Tom