[Exim] problem with nested condition

Hi,

try to save mails, where spam-status is below or equal "1.0" AND
message_size below !1M".
(HAM mbox for bayesian filter)
this one doesn't work:
condition = ${if and { \
                or { \
                    {match
{$header_X-Spam-Status:}{\N.*hits=0\..*\N}} \
                    {match
{$header_X-Spam-Status:}{\N.*hits=1\.0.*\N}} \
                    {match
{$header_X-Spam-Status:}{\N.*hits=-.*\N}} \
                } \
            {< {$message_size}{1M}} \
            {yes}{no}}}

exim_mainlog:
failed to expand condition ..[snip]...for spam_deliver_router router:
subcondition in {} expected inside "and{...}" condition

I've tried several things but all fails :-(
Additionaly I want to add another AND-condition, so that this message will
not saved twice. For this I add a special X-header by the router.

Thanks for your help
Wolfgang