The question doesn't really make sense, functionally.
If you always want to translate to the same language, maybe you should look at providing translation links instead. Assuming you're using a CMS of some kind, just go to the main Google Translate page, give it some URL/language combination and submit. You'll end up at something like this:
...which is a link translating
http://example.com from English to Japanese.
Then, in your CMS template, replace the value of the
&u query parameter with the URL of the current page, URL-encoded.