re-add deleted extended logical partitions?

[David Coe <dcoe@overlord.com>]

Help!  I inadvertently deleted (using fdisk) two ext2 partitions that are
in an Extended primary partition (i.e. they were /dev/hda7 and /dev/hda8).

I've done nothing since then but a lot of reading.

Can I safely add them back using fdisk or sfdisk (or cfdisk or
something else?  I know their physical locations and sizes
and have verified (using a nice tool called gpart) that they're
apparently still intact. 

If not, how can I find and update the extended partition table
without modifying the partitions' contents?

Thanks in advance.