I suspect I'm in the wrong forum. If so please direct me.
I'm trying to do the song, "Then You Can Tell Me Goodbye" by the Casinos - early sixties I think.

It's really just a basic I-VI-II-V but before coming back to the verse they slip in a I7#9 chord that really makes the whole song.

C//Am//Dm//G//C//Am//Dm//G,C#7#9 doesn't work
I even tried adding a 9th measure.

Any help at all!!