Script problem

I have been trying to make a script that print something on the screen, but when I play my wad and activate the script, it says:
P_Startscript: Unknown script 4

What's that supposed to mean? I wrote :
script 4 (void)
{
Print (s: "\A door opened...");
}

What did I do wrong?

Did you save your new compiled BEHAVIOR lump with the level?

Yep, the behavior is saved and it still don't work. I want that when the player use the open door button "e" for me, on a computer, it opens a door by Door_Raise and make a message appear on the screen. The code inside the script is ok, I checked it over and over and I didn't found anything wrong.
I hate it because it's the only thing left to do on my map.

Never mind, I found another way to finish it. My first map is finally finished. Wooohooo !