RE: In which codeunit i can write code when any insert / Modify for in NAV tables ?
So you want to log values un a third-party table each time data is Inserted / Modified in a NAV table like Item, Customers, Shipping addresses etc?
Then you just need to put your code in the OnInsert / OnModify trigger of each Table.
Each table in NAV has OnModify/OnInsert/OnDelete trigger.
If you want to log for a specific field then you need to put your code in the OnValidate trigger of that field.
If you want to create kind of more generic logging system then you can analyze the CodeUnit 1 ApplicationManagement which contains more global triggers like OnDatabaseInsert for example which is fired each time something is inserted regardless of the table. (but be careful as it is a core codeuinit of Nav and each change should be thouroughly analyzed)
Regards,