Your could look at using a 'whirlygig'.
Simply fork and do the copy in the child while the parent shows that it is still running. When the child ends it will send a SIGCHLD. Or do the copy in the parent and kill the child when you finish.
Or in the parent you could periodically check the size of the destination file (though I think windows keeps it at 0 until the file is done) and display that somehow.