how to config the "open_basedir" in apache2

[lnfreish]

I just want to generate mass virtual hosts, so I use

NameVirtualHost 192.168.0.1
<VirtualHost 192.168.0.1>
ServerName *
VirtualDocumentRoot d:/htdocs/%0/htdocs
AddModule php4_module c:/php/sapi/php4apache2.dll
AddType application/x-httpd-php .php .php3
</VirtualHost>

Now I expect everyone can only open their "htdocs" directory, so I use it like
<VirtualHost 192.168.0.1>
ServerName *
VirtualDocumentRoot d:/htdocs/%0/htdocs
php4_admin_value open_basedir d:/htdocs/%0/htdocs
AddModule php4_module c:/php/sapi/php4apache2.dll
AddType application/x-httpd-php .php .php3
</VirtualHost>

I found it can't work normal, who can help me? thanks.