Darren,

>select b.* from detail d join barcodes b on d.po_num = b.po_num and d.style = b.style where d.wo_num = 123456 into cursor csrBcodes

Since you are only selecting columns from barcodes, try rewriting it:

select b.* from barcodes b ;
   inner join detail d
   on b.po_num = d.po_num and b.style = d.style and d.wo_num = 123456 ;
   into cursor csrBcodes