Displaying a message box

Hello all,

I would like to show a message box with an "OK" for the user to dismiss during setup.

I had tried add a vbScript to do so:
1. Created a file and named script.vbs
2. The file has one line - MessageBox ("The text I need", WARNING);
3. Added a Custom action Before the Welcome screen and named it Exfn_MessageBox
4. Set the File Name to where my .vb file is

When the installation reached the point where the script should it run it showed an error message saying "Error 1720. There is a problem with this Windows installer package. A script required for this install to complete could not be run. Contact your support personnel or package vendor. Custom action Exfn_MessageBox script error -2146827264, Micros..."

What have I done wrong? Is there a better way to create a message box?

Thanks,
Asaf