CakePHP mathematic-calculation field?

(Database structure like http://stackoverflow.com/questions/1545764/cakephp-select-default-value-in-select-input)

So, I have two tables in CakePHP: Trees, and Leafs. Every Leaf has a tree_id for its corresponding tree. Every leaf also has a numeric value. The default view that I baked for trees just lists all the trees in a table. Is there a way to add a dynamic column to that view's table that SUMS all the leafs of that tree and displays the sum in the table, as well as another field showing the number of leafs a tree has?

example:

Leafs

Id   |  Tree Id  |  Leaf value
-----+-----------+---------------
24   |  1        | 19
70   |  1        | 33
121  |  1        | 30

Trees

Id   |  Tree  |  Number of leafs  |  Sum of leafs  |  Actions
-----+--------+-------------------+----------------+-------------------
1    |  foo   |  120              |  7270          |  View Edit Delete
2    |  bar   |  72               |  4028          |  View Edit Delete