whmcs and translated content redirect

Hi

We use transposh for content translation and this creates a url with /languagecode

per example snelgoedkoop.nl/en

we also use whmcs and the menu to the integration page is fine, however if one orders and click the order button the url is back to default without trailing lang code.

As English people dont speak my language thats a bit sad.

I was thinking that there are two solutions:

1: if posible update the plugin to deal with this

2. use a rewrite rule with referer, if referer is mydomain.com/en/ then append language=English to the whmcs system url, that would enable whmcs to serve english content

if this is the way to go i sipose that rule should be placed in the whmcs server root, could u say how that should look that rule?