I've been through a list of all the songs in Harry Potter and the Goblet of Fire (movie), but this particular song does not appear to be listed as one of them. It is played very briefly in HP4 just after Ron is rejected by Fleur. The Durmstrang ship is shown for a minute, then the entrance to the Great Hall for the Yule Ball, just before we see Ron complaining about his dress robes. It is played at approximately 1 hour 14 minutes in the film. I apologize for not being able to find a movie to link to, but I can't find this particular scene online for some reason. You will notice it's rather like a waltz and the fact I can't identify the name of the song is very annoying!
A video with the music in the background can be found here:(my apologies for the poor quality sound, but it gives you an idea of the music and, if you have access to the movie, it is just before this scene).