[exim] acl variable

Hi,

I have a simple situation. These lines from the smtp data acl...

# Pretty good attachments
   warn    set acl_m5 = 1
           demime = pdf:doc

# Media greater than 1.5 MB
   warn    message = X-Cheetah-Media: Large
           condition = ${if ! eq{$acl_m5}{1}{1}}
           condition = ${if >{$message_size}{1536k}{1}{0}}
           demime = jpg:jpeg:pps:ppt:gif:png:wmv:mp3:mov:asf:asx

I don't want to tag emails that contain pdf/doc AND media attachments.
But this doesn't work. Any hints? Is there a way to express NOT using
the demime like this...

    demime = jpg : ! pdf : ! doc : jpeg

Thanks,
Craig Jackson