pf rdr rule question

[Gót András]

Dear All,

I'd like to have the following ruleset, for pure-ftpd passive port 
range:

---
ftp_pasv_start="X"
ftp_past_end="Y"

rdr on $netif inet proto tcp from any to $internalip port 
$ftp_pasv_start:$ftp_past_end -> $internalip

pass in quick on $netif proto tcp from any to $internalip port 
$ftp_pasv_start >< $ftp_pasv_end keep state flags S/SA
---

My problem is that I got " unknown port $ftp_pasv_end" errors when I 
try to load it with pfctl. Of course I checked the manual and there's 
not much about macros in the nat rule section. Anyone knows what did I 
do wrong or missed in the manual?

Thanks,
Andras