Purchase order, print program.
Prereq : create print program and config in NACE
When you plan to do some coding after your repeat the output
1. send email to vendor
2. do some coding as soon as you push the output again the codes below are important

    IF nast-nacha = '5'. "EXTERNAL SEND + TCODE + AND WHEN SAVING
      IF ( sy-tcode = 'ME9F'  AND sy-xcode = '9AUS' ) OR
         ( sy-tcode = 'ME21N' AND sy-ucomm EQ space ) OR
         ( sy-tcode = 'ME22N' AND sy-ucomm EQ space ) OR
         ( sy-tcode = 'ME23N' AND sy-ucomm EQ space ) OR
         ( sy-tcode = 'ME28'  AND sy-ucomm EQ space ) OR
         ( sy-tcode = 'ME29N' AND sy-ucomm EQ space ).