Pull user data from custom table

Is it possible to fetch user data from a custom table summarizing (or not) on certain field. From what I have read and how installation worked seems it is not (but i might be wrong). I have a custom table
– which presently do not have user_id [i am using some other unique id but have no problem in adding a user id]
If it can be done by some way then:
– user|date|amount -> so can i easily sum amount for an user or summarize based on rules??

Presently for each user am using php queries but if it can be done for all user when admin is logged in, it would be real time saver for me..!!!

http://wordpress.org/extend/plugins/amr-users/