Is it possible to download a bash script and execute it from a preseed file?

I'd like to prepare an iso for unattended installation. So I generated a preeseed file to run through the installer automatically. Is it possible to download a bash script with wget and run it with bash directly in the first user's homedir (where the first user is the user account created by the installer)? What would the commands in the preseed file look like?

Here is how:

d-i preseed/late_command string in-target wget -P /tmp/ $server/script.sh; in-target chmod $+x /tmp/script.sh; in-target /tmp/script.sh`

Put this line into a preseed file and you can do everything in your system you are familiar with bash.

You have to replace $server with a webhost or a local ip of course.

You can also use:

d-i preseed/run string run.sh

The run.sh file must be stored in the same directory from which the preseed file was downloaded.