I run both locally by having a path that runs php 5 there on in, i.e. http://localhost/php5/
This is from my apache conf
# CGI
ScriptAlias /php4-cgi c:/winfiles/php/php.exe
ScriptAlias /php5-cgi c:/winfiles/php5/php-cgi.exe
# most scripts will be php 4
Action application/x-httpd-php /php4-cgi
AddType application/x-httpd-php .php .phtml
<Location /php5>
Action application/x-httpd-php /php5-cgi
</Location>
EDIT: just realised I completely skipped the asked question, which I seem to be getting really good at, so to simulate your hosting condition you could modify the above to be something along the lines of:
# CGI
ScriptAlias /php4-cgi c:/winfiles/php/php.exe
ScriptAlias /php5-cgi c:/winfiles/php5/php-cgi.exe
# most scripts will be php 4
Action application/x-httpd-php /php4-cgi
AddType application/x-httpd-php .php .phtml
# oh php 5 with your aspirations to javahood, make my dinner
Action application/x-httpd-php5 /php5-cgi
AddType application/x-httpd-php5 .php5