[Exim] Problems with a condition statement

Hi,

I am have problems getting an "or" condition statement to work.

I know this works:
${lookup{$local_part}lsearch{/usr/local/exim/etc/spamassassin}{1}{0}}

And I know this works:
${if >= {$message_size}{20M}{0}{1}}

But I don't seem to be able to get an "or" statement that combinds the
two to work. Example:
$(if or
{{eq{${lookup{$local_part}lsearch{/usr/local/exim/etc/spamassassin}{true}{false}}}{true}}{eq{${if
>={$message_size}{20M}{true}{false}}}{true}}}{0}{1}}

Basically, I want the string to return a 0 if the message is 20M or
bigger or if the local_part appears in this file. Please help.

Thanks,
           Carl