[AccessD] A2003:Rename Files in a folder

Hi all
 
I have to loop through a folder and rename all the files in it to have some text
as a prefix
 
For EG there may be a folder C:\CoolFolder
In it may be 5 files or 5000 files that are all sequentially numbered and named
like...
1012.pdf, 1013.pdf, 1014.pdf etc etc
 
What I need to do is loop all the files and add a prefix such as "inv" so the
file names become 
inv1012.pdf, inv1013.pdf, inv1014.pdf etc etc
 
Any pointers - anyone got any file renaming snippets they'd care to share?
 
many thanks in advance
 
Darren