Help with locales in sencha architect

It's about locales...
My question is how do i insert functions in values. This is what it suppose to be :

Code:

---

{

xtype: 'textareafield',

label: I18n.t('items.mainToolbar.items.locale.label'),
value: I18n.locale,
readOnly: true

}

---

But, the result is different :

Code:

---

{

xtype: 'textareafield',
label: 'I18n.t(\'items.mainToolbar.items.locale.label\')',
value: 'I18n.locale',
readOnly: true

}

---

His there a better way to do that ?