installer that copies itself while executing

is there any reason why this would not work ?
I am trying to get the executing installer to copy itself

CopyFiles /SILENT "$EXEDIR\${myExecutingInstaller}.exe" "$DESKTOP\${myExecutingInstaller}.exe"

many thanks
g

This worked on my comp

CopyFiles /SILENT "$EXEDIR\${APP_NAME}.exe" "$DESKTOP\${APP_NAME}.exe"

  IfFileExists "$DESKTOP\${APP_NAME}.exe" 0 +2

  MessageBox MB_OK "${APP_NAME}.exe exists" 

this is a code snippet which for some odd reason always says the file does not exist 🙁
what stupid thing have I done ?
FYI, $EXEDIR\${FILETITLE}.exe

let me try this again
WithinInternetCacheFolder:
;copy exe to the desktop
messagebox MB_OK "Within Internet Cache Folder"
CopyFiles "$EXEDIR\${FILETITLE}.exe" "$DESKTOP\${FILETITLE}.exe"
messagebox MB_OK "Copied $EXEDIR\${FILETITLE}.exe to $DESKTOP\${FILETITLE}.exe"
sleep 1000

IfFileExists "$DESKTOP\${FILETITLE}.exe" exist noexist
exist:
messagebox MB_OK "${FILETITLE}.exe exists"
goto done
noexist:
messageBOX MB_OK "${FILETITLE}.exe DOES NOT exists"
goto done

FYI, $EXEDIR is the Temporary internet cache directory for Internet Explorer

would that make some kind of difference ?