Creating a command to launch the last downloaded version

I'm using (well.. trying to use) Ketarin to maintain the list of my used application, and I want create a batch file with the name of the last downloaded version in the same directory of the application.

So I can configure the good WPI (www.wpiw.net) interface only one time to use as target the command file.

Let me explain with an example.
I'm using a directory structure like this:

H:\WPI\Install\Internet\eMule\

and in the directory I would have:

eMule0.46b-Installer.exe    <--- old version
eMule0.48a-Installer.exe    <--- old version
eMule0.49c-Installer.exe    <--- current version

emule.cmd                          <--- batch file to launch the current version

In the commands tab of Ketarin I wrote in the "Execute after downloading"

echo {file} >> {root}{dirbase}\{category}\{appname}\{appname}.cmd

But this is absolute and not relative so is not possible to burn a CD and use WPI to reinstall all my software.

I have tried to use {url:ext} or {url:basefile} but it seems that they are empty when called in the post-processing

Please give me any advice you know.

Thank you

Marco (Italy)