Start a bash file from GUI

I'm asking your help: I'm trying to start a bash file directly from the desktop/gui, in the same way on Windows .bat files.

I've created a file called update.sh like the following one

#!/bin/bash
export PATH=/usr/local/bin:$PATH
svn update ~/blitzmax
svn update ~/blitzmax/bin

I've made it executable with chmode +x update.sh
The file is on the desktop, but when I double-click on it, the OS opens TextEdit...

I want to run it with the double click

Thanks in advance.

How's about : http://www.macosxhints.com/article.php?story=20030728055235121

Great.
Many thanks!