Found it, I think.
http://www.songlyrics.com/song-

Al Dubin / Joe Burke)

I'm dancing with tears in my eyes
'cause the girl in my arms isn't you,
dancing with somebody new
when it's you that my hearts calling to...

Trying to smile, once in a while,
but I find it so hard to do.
For I'm dancing with tears in my eyes,
'cause the girl in my arms isn't you....