Excluding stack trace from Layout

Hi,

I have tried to search for an answer here and tried to understand the documentation but can't say I have been successful.

I'm using this configuration value for the layout pattern:

<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="%date %newline [%thread] %newline %-5level : %message %newline" />
</layout>

This is too much information.  I don't want the stack trace, only exception.messge and exception.InnerException.

How do I specify that in the layout?  

Thanks in advance for helping.

Habib