Support for setting Aggregator IP/ASN in BGP Updates

Hi all, we are manually announcing and withdrawing prefixes by disabling and enabling a static protocol: E.g: protocol static prefix{     ipv4;     route 1.2.3.0/24 blackhole; } Is there a way to manually set the BGP AGGREGATOR IP address or ASN for the resulting announcements or withdraws? Cheers, Clemens