need help duplicating the files from one folder to another

This is the code I have:

tell application “Finder”
set fromFolder to fileStructureToCustomer & “Proofs:” as alias
set ToFolder to fileStructureToCustomer & “PictureShow:” as alias
duplicate every file of folder (fromFolder as string) to folder (ToFolder as string)
end tell

but I am getting the error

File Macintosh HD:users:Rupert:desktop:baird:customers:Chris Humphreys:Proofing:Tracy Scott Baird - Tracy Baird:Proofs: wasn’t found. (-43)

What I don’t get is that it acts like it is trying to find the file named above in error message, but that is the folder. I want to copy everything from the fromfolder to ToFolder