rewrite backend http to public https

[thedaver]

I'm having trouble between mod_rewrite and mod_proxy for my Apache 1.3.22 config.

I have a backend webserver without mod_SSL enabled on the box.
I have a public SSL-enabled webserver.
I am able to proxy HTTP the backend through public ok.
I want to have public present backend's passthrough as SSL'd
HTTPS.

I'm stumped.

Working Ruleset so far:
-----------snip httpd.conf-----------
RewriteEngine on
RewriteRule ^/register(.*)$

http://10.0.0.72/cgi-bin/signup.cgi$1

[P]

Is there a way for public server to present HTTPS to browser when backend's source HTML is not SSL?