Automatic disklabeling after resizing partition

[Mohd Hisham Mohd Omar]

Is there any way I can invoke automatic disklabeling like when you first 
install Openbsd on your system? I can't figure out the correct start and 
end sectors after resizing my NTFS/FAT32 partitions using Partition 
Magic. I always messed it up after doing manual disklabel in which 
afterwards Openbsd cannot mount the resized FAT32/NTFS. Openbsd 
(always!) correctly detects existing partitions when it first installs 
so could I let it do the job for me after?

Thanks.