Resize automatically the height of a field according to the number of lines

Hi,

I am looking for resizing automatically the height of a field according to the number of lines with the fieldFull method.

Here is the script I tryed:

if (event.fieldFull) {
	//app.alert("The text field is full.\rWe are going to increase its height to be able to continue typing.");
	var nomChamp=event.target.name;
	this.resetForm([nomChamp]); // Reset field to lose focus
	var aRect=event.target.rect;
	aRect[3]=aRect[3]-event.target.textSize*1.16;
	event.target.rect=aRect;
	event.change=event.changeEx;
	this.getField(nomChamp).setFocus();
}

 That works approximatly because I lose the focus of the field and I need to type on this field to continue typing... Is there a way to avoid that?

P.S.: The 1.16 line spacing ratio is used for the Helvetica font.