[Rtano]

Does anyone know how to make a windows update (downloading and installing only the critical patches) via a script..?

Or i have to download the %HOTFIX%.exe and then execute it by script?

[Innominandum]

I don't know of a way to download hotfixes via script yet, but i'm guessing that you could write a script to parse the mssecure.xml file (microsoft's hotfix list)
and download and install the hotfixes.

Or , you could download them yourself and use this script to install the hotfixes on local and remote systems.

You could find some information here.