world hardest song to find

hi, everybody.
that's years i'm looking for a song without success. and it's cause the poor information i have about it. this is the situation: someone gave a music cassette to my brother about 10-15 years ago. it contained the lp "look sharp!" by roxette in the side A and the lp "i'm your man" by leonard cohen in the side B. both lp's are from 1988, so that gives an idea of the time i'm speaking about. but (and this is the point) at the end of the side A there was about 30 secs of another song that i think didn't belong neither to roxette nor to leonard cohen. and that song delighted me. the problem is that i've lost the music cassette and all that i have are weak remembers of the melody. it began with a voice repeating about 3 times "all night long" (or something like that) and, after, the song acquired a faster rythm, with a delightful melody. but, even, i can't assure the singer was a man or a woman, because the voice wasn´t too clear to have a certain idea.
and that's all. i suppose it's a song of the 80's, i have looked ont the internet lots of entries with "all night long" and downloaded lots of songs with that title, but none of them was the one i'm looking for. i don't know what else can i do, and i imagine i will never listen to that song again in my life.
it's a pitty so, any help will be REALLY WELCOME

thanks

[citcrasniper]

Did you try all night long by lionel ritchie