I think it is right but, after getting that value i need to group it, and as far as i know function fields can not be group.. Thanks for the reply :D

You can group it if you define it with store=True. But then you have to consider to use triggers for the updates.

That's one of my problem, i use fields related with store true, my problem is i need to save the form where i'm getting the fields and then edit it again ang work on the form where my fields related is located.. What i want to have is that i fill out my form then go to one2many form then fill out again , and go to one2many form again, fill out then save, save, save.. But if i do this using fields related with store true it will not group accordingly because my fields related did'nt store the value.. Many thanks to you :)

Use the function field with store=True. For related fields this is not possible afaik.

If i use function field with store true, do i need to save the form first fro the store true to be triggered??

Yes, when the form is saved, then the function-method and the store are triggered.