I have a session with tfacr200 like main table.
This session has a button to call text manager, but when I return to the text manager the field tfacr200.text has 0 and tfacp200.text has the number of the text.
My session is a copy of another one to tfacp200 like main table, but I change the main table in the new session.

In order to solve my problem I have written the following:

choice.text.manager:
before.choice:
tfacp200.text = tfacr200.text
after.choice:
tfacr200.text = tfacp200.text


Where can I change the field text asociated to the button?

You can check what text field (s) are active in the Sessions specific pull down menu - there is an option for 'Text Fields'. Check that this is not showing the tfacp200.text, it should be set to your tfacr200.text.