Conditional custom fields permalink

Hello, I’m using permalink manager pro, how can I set a custom post type permalink based on custom fields values.

Example: two custom fields: A and B

if(empty(A)) return B;
else if(empty(B)) return B;

return post_title;

I tried with permalink_manager_filter_default_post_uri but it’s no use. This hook only works when updating posts but not working when creating new posts because it’s fired many times before all custom posts/post meta are updated。