Can you give more detail at all, withotu compromising security ?
Are we talking intranet environment on Windows IIS with ColdFusion added into the mix ?
Are the servers on the same hardware LAN or part of a WAN ?
What level of access do you have and, crucially, how far along with ColdFusion are you ?
I'm sure you are familiar enough with the relevant information to know what I'm looking for here.
Just to bounce a simplified concept around, what about supplying a link to a page which has a simple upload feature built in that targets the necesary directory ?
There are a number of possible methods that come to mind to help you get over your cross-server issue. Most of them rely to one extent or another on network permissions or acces rights and you could do anything from write a script to copy the uploaded files from their original directory to the desired directory on the other server or you could, well, hang on a bit. Before I go off on one about what you could do, let's try to work withinn the parameters you have available.
I'm on and off line quite a bit at the moment (very, very busy) but if you drop a bit more detail into the mix I'll see what I can come up with for you, provided you aren't up against the clock yourself, in which case someone else will have to step in.