looping linked objects

Hi all,
I have a problem with linked objects, I don't know how to cycle on them, maybe someone has already faced this requirement.
I have two custom objects, obj1 and obj2, both contain links to another object (obj3).
Is there a way to create the same links I have in the obj1 into the obj2?
I am able to create the first link, but I don't know ho to cycle in the source list.
Example of code that works only for the first linked object:
1) Set a new variable, reference to Object of Type obj3
2) Set the variable, run on link in obj1, to the obj in the source link
3) Create a new link in the destination object passing the variable.
Thanks,
Cristina