Synchronizing contacts between companies

Hi.
I'm working in a company which has 7 companies inside Dynamics NAV. Most of them are only using accounting module. They've just created a new company which it's going to work with a own module based on contacts module. As they need to work with contacts already created in the "master" company, I need to share them between companies.
I thought about using "DataPerCompany" property but I read about many problems that might occur. Then I look into about how to synchronize companies and I found the code below:

Comp.FIND('-');
REPEAT
  IF Comp.Name <> COMPANYNAME THEN BEGIN
    Item2.CHANGECOMPANY(Comp.Name);
    Item2.COPY(Item);
    If not Item2.insert THEN
      Item2.MODIFY;
  END;
UNTIL Comp.NEXT = 0;

where "comp" is a record from 2000000006 table "Company"

I'm not pretty sure that how to use this because contacts can be created by standard Contacts Form or with a Form from that own development, which uses .INSERT and .VALIDATE methods. Then, must I use this code in OnInsert trigger? in OnValidate trigger? In both?
Regards.