mv command behavior

[lists at dwsasia.com]

Hi, I don't know if I already sent this question or not, my server  
died before, and I havn't been able to receive the mails for a while.

I want to move the files from one dir to another, but only if they are  
newer. So I do:

mv -u /tmp/dirA/dirB /dirC/dirB

Meaning moving it from being a subdir of /tmp/dirA to be a subdir of /dirC.

The first time it works, but the next time it will end up being like this:

/dirC/dirB/dirB :(

Could I use the "cp -ru" instead with some other flag to remove files  
successfully copied?

/Peter