calendar synchronization among groups

I've used Palm desktop for ages, but have now reached the point at which I'd like for my administrative assistant to be able to adjust my schedule and for me to become aware of that on my Treo 700. If we could do the same for my partner, that would be ideal.

Does anyone know of, or use a program that will sync with either Palm Desktop or Outlook (without an Exchange server) in this manner? I'll switch programs, if that's necessary.

Thanks for any help,
D
.