Changing current language in Orbeon

Hello,

I need to change the current language in my Orbeon forms programmatically. The reason for this is that I have a service that provides translations to our XForms based forms. I load translations using <xforms:submission> into 'fr-form-resources' instance, where Orbeon originaly stores control labels.
Later, these translations made available as following:
<xxforms:variable name="form-resources" select="instance('fr-form-resources')/resource[@xml:lang = 'fr']"/>

Everything is fine, labels are translated and shown, however Orbeon's current language defaults to English ('en'). As a result such controls as Calendar and validation messages are always in English. I know about using 'fr-language' in URL, but this is not convenient for us. Is there any way where I can set current language to Orbeon using XForms? I tried to set 'fr-language' using
<xforms:insert context="." origin="xxforms:set-request-attribute('fr-language', 'fr')"/> in my forms, but this also didn't help me.

Thanks a lot in advance.

-Rovsh