Shoutbox

Hi,
I'm french and my english isn't very good..
I will try to ask my question..

I have an xml window and I want change caption's value when it opens.
I try to use SetControlText() but it returns an error

here my code :

code:

---

case "AboutOsef":
            var Wnd = Window('Interface.xml', 'about');
            Wnd.SetControlText('website', url);
            Wnd.SetControlText('version', v);
            break;

---

and the error's translation (my error is in french..):

code:

---

Error: 'undefined' has the value Null or isn't an object..
       Line: 62. Code: -2146823281.
Function OnEvent_MenuClicked returned an error. Code: -2147352567

---

Thx.

EDIT: the code is in OnEvent_MenuClicked() and the line 62 is "Wnd.SetControlText('website', url);"