Translation with variables

[Daniel]

How do I make a string with a variable translatable?

Say in English I have

"Press " + X + " to find."

But for a translation to other languages it might not be sufficient to 
translate "Press " and " to find." and string them together in the same 
way as in English. So, maybe it is not sufficient to do:

_("Press ") + X + _(" to find.")

Or is it up to the translator to figure this out (maybe the added spaces 
are an indication for there being a particular context)?

Daniel