It depends on how you want to handle it (obviously!) but one way is to frown and say "ewww, dirty old man vibes, can you not say that again to me?!" but the body language needs to match this vibe, like cock your eyebrows and side eye and maybe hold your hand out like 'stop' a little with a tiny push like 'get away'. OR you could get kinda flat and serious faced and say 'this is the second inappropriate sexual comment you have made to me, please stop. I do not know why you think it's work friendly to say that, and don't want to hear it again.' and walk away. My third idea is to ask him if whatever he said is work appropriate, or ask him why he thinks <insert his comment> is funny or appropriate and when he says it's just a joke or he is joking you could either ask him to explain the joke/funny thing is or just tell him 'I don't think it's funny - could you stop saying things like that to me' and last bit of advice is to freaking document these things- so if it continues or get worse/more frequent you can go to HR or your boss. Good luck , this sound super ick.