how to copy a file to a directory ,where file and dir are sent as args to a function?

Hi all,

I wanted to know how i can copy a file to a directory and then verify if that file is completely copied or not?
Now the issues here is that the dir and the source file are to be sent as arguments to a function( this function should actually copy the files to a dir, then check if its completely copied)

I dont want to use the

if [ -e <filename>]
option then figure out if the file exists in the dir or not....
Reason being i am giving a progress bar that actually calculates the % of completion....
I have written scripts that do the job ,but a pre-requisite is that a file already needs to exist in the dir, then to this file i can copy my source file.

But my idea is to have no files in the targeted dir ,and when the cp is done the source file should exist in the destination dir!!!!

please help!!