Database scheme for product tracking
Normally what you would have is something like this:

CREATE TABLE Product (
ProductID,
Name,
Description
) ;

CREATE TABLE Order ( /* Shipped products */
OrderID,
ProductID,
ShippedDate
);

CREATE TABLE User (
UserName
) ;


And here's the essential table you need. This establishes a many-to-many relationship (commonly known as an intersection or bridge table) between Orders and Users:

CREATE TABLE User_Order (
OrderID,
UserName
) ;


For every order you would insert one record into the User_Order table for every user that can track that order. So you would have something like this:

OrderID         UserName
-----------------------------
1               joe
1               jane
1               john
2               joe
3               bill
3               jane