[exim] redirect transport $rcptxxxx?

Hi all !

Trying to figure out how to 'just add a header' in a message tagged by MailScanner als SPAM. Can't seem to figure out how many
recipients are checkt during 'one transport'. At first I thought I might use:

"$received_for: If there is only a single recipient address in an incoming message, this variable contains that address when the
Received: header line is being built. The value is copied after recipient rewriting has happened, but before the local_scan()
function is run. "

But what would happen to messages with multiple recipients ?

Perhaps there is another way to do the same thing ..... my router current looks like this:

outgoing_check_for_spam_header:
 driver                = redirect
 debug_print           = "R: Checking: Is message a spam message?"
 allow_fail
 allow_defer
 condition             = ${if match {$h_X-MailScanner-SpamCheck:}{spam.*}{yes}{no}}
 data                    = * What should go here .. ? *
 headers_remove      = X-Spam-Flag
 headers_add           = X-Spam-Flag: Yes
 repeat_use            = false

Any one who can shed some light on this ?

bye,
Chris