Resize edittext in UI

I try to change the length of an edittext depending on a checkbox.

This is my code so far:

FormatSingle.z3 = FormatSingle.add('group');
FormatSingle.z3.Titel = FormatSingle.z3.add('edittext',undefined,"Zeile4");
FormatSingle.z3.Titel.characters = 15;
FormatSingle.z3.ifSub = FormatSingle.z3.add('checkbox',undefined,"Unterzeile");
FormatSingle.z3.ifSub.onClick = function()     {          if (this.value == true)          {               FormatSingle.z3.Titel.characters = 23;               w.layout.layout(true);               w.layout.resize(true);          }          else          {               FormatSingle.z3.Titel.characters = 15;               w.layout.layout(true);          }     }

('w' is my window, 'FormatSingle' is a defined variable (group))

For the layout-commands I tried multiple versions, like this one; without the 'true'; not with the 'w' but with 'FormatSingle', but the only thing happening (if anything happens) is that other Elements of my window move slightly around.