How to update TextBox height

Hi,
I’m trying to make an editor like the android SMS editor described here:
http://developer.coronalabs.com/forum/2013/02/27/create-editor-native-sms-editor-why-cant-i-do-something-simple

For this, I need to update the textbox height or an auto-height mechanism.
How can I update textbox height ?
When I do it with mytextbox.height or mytextbox.contentHeight, then the textbox is drawn with a random height.

Regards
David [import]uid: 223645 topic_id: 36918 reply_id: 336918[/import]