setting php_admin_value

Hi all, ok, I am writing an apache module that dynamically figures out virtual host variables for data locations for my users. I need to be able to set the php_admin_values for each request so that those values get passed through to php and take effect for each request. Normally, this would be static inside the apache conf file using the php_admin_value directive. Does anyone here know how I could set these variables dynamically ? Do I have to load the apache configuration tables and change it manually ? or can I set a particular environment variable that gets read by php ? Thanks, Tim.