Set Analysis problem

[carlos13]

My idea is to select any field of the Year (only one, e.g.:'2012') and obtain the total up to that year. In the expression i wrote this:

Count({<Años={">=$(=(Años)) <=$(=(Años))"}>} DOC_IDENTIFICACION)

but does not work. So i need a little help with this.

I will be very grateful with any response and for your time. And excuse my english, is not very good.

Regards.

Carlos