access for levels

[masons]

Hi,

on my site I serve levels of people in an organization,
lets say level 1 2 and 3

For each level there is a category forum made, with sub forums in them.
Now, at the moment each forum per category has a password, which is a hassle.

So I need to make it work like this,

a level 1 can access all open forums and level 1 category forums
a level 2 can access all open forums, level 1 and level 2 forums
a level 3 can access everything.

How can I achieve this?