I have an other problem.
I need to create a new record with this calculation "1" for the first, "2" for the second record etc...
When this number is reached, I need it to start over from 1.
For example I put "4" in field "number"
Records: 1->1, 2->2, 3->3, 4->4, 5->1, 6->2... etc
Do you know how to do that? Reset the "extend" fonction maybe?