script to run via cron from Plesk

Hi, we need a script to run via cron from Plesk. It should run a check on the EAN13 column of our DB and insert the missing ZERO numbers at the top of the code to bring the digits "always" to 13 numbers.
Example:
Ean in DB with 8 digits = must insert 5 "zero" numbers (0) at the top
Ean in DB with 9 digits = must insert 4 "zero" numbers (0) in header
Ean in DB with 10 digits = must enter 3 "zero" (0) numbers in header
Ean in DB with 11 digits = must enter 2 "zero" (0) numbers in header
Ean in DB with 12 digits = must enter 1 "zero" number (0) in lead

payment and/or Milestone ONLY after successful completion.