There are some things you're going to need in this scenario -- First off, is this a code or a cipher?

Codes are inherently harder to break then ciphers which is why most diplomats spend a great deal of time trying to "acquire" code books from other embassies/consulates/ships/etc. Some codes have alphabetic entries to spell out uncommon words (like towns/names) while others will send a null code group like 1111 or 9999 to indicate start/stop using the first letter of the code word to spell and go back to using the actual code meaning.

If it's a cypher (or cipher . . . different people spell it different ways), then you need a sufficient amount of enciphered text to begin an attack. Four ten-word sentences, unless there's a significant amount of overlap, is unlikely to be sufficient unless it's an extremely simple code. As a former cryptanalyst, I could buy four enciphered paragraphs (say, 100 words per), as that would allow for possible duplication of words or phrases -- this is usually the most direct way to break into a cipher. Again, the more complex the cipher, the more recoveries using the exact same system are required to get the first break which will allow your cryptanalysts to have a chance to recover not only the message but the system being used. After that, it gets down to boring stuff like letter frequency use, identifying simple words, etc. (and this is assuming you know what the original language of the cipher is to begin with). If each of the four passages is set with a different key, (1st being A=R, then A=Z, etc.), then I'm not sure even a paragraph is going to be sufficient.

Sorry if I'm getting too far down in the weeds, but if you're wanting to make this fairly realistic, you'll need to keep things like that in mind. If you want more help, I'd be happy to assist.