Pre-render script and netrender

Hello,

I try to use a pre-render script with a netrender and backburner.
in the render scene dialog, I put a file in the pre-render script slot. (this script create a box and change sampling parameters).
- if I make a local render, it's ok, the script start, create the box, change sampling parameters, and after, frames are rendering.
- if I check "net render" and send the job to backbuner, the script don't create the box , but change the sampling!!!! In the monitor screen I can see the name of the pre-render script. but it seems don't excute all scripts command.
Do you know the method to use pre-render script and netrender?

thank you very much and sorry I don't speak very well english
Bruno