LyX ⇒ Reference Style Problem

[christinagt]

Hi, I'm new using LyX and I want to use it for my thesis, but I have a problem, I have to use a special references style that I have not found in any BibTex style.

I’m using Natbib with Author-year and a file with my references *.bib, the style that I’m using now is plainnat, and the references look like:

1. Sección ejemplo
Aquí va una cita: [Last, 1900][Nuñez, 2008][W3C, 2011]

Referencias

First Last. A ctitious journal article. Journal of nothingness, 2:12, 1900.

Eduardo Nuñez. Titulo de la tesis. Escuela, 2008.

W3C. algo, Mayo 2011. URL http://www.w3.org/.
Respectable Writer. A silly book. PublishCo, Somewhere, 2000.

But I need that they look like:

1. Sección ejemplo
Aquí va una cita: [Last, 00][Nuñe, 08][W3C, 11]

Referencias

[Last, 00] First Last. A _ctitious journal article. Journal of nothingness, 2:1_2, 1900.

[Nuñe, 08] Eduardo Nuñez. Titulo de la tesis. Escuela, 2008.

[W3C, 11] W3C. algo, Mayo 2011. URL http://www.w3.org/.

With square brackets, only the first 4 letters of the first author’s last name, a comma and the last two numbers of the year. And the references have to have the same format at the begining. The Style alpha is very close of what I need but it doesn’t support URLs.

I would like to know if it would be easy to modify the Style plainnat and make it do what I need or if there is another way to do what I need.

Thanks and sorry for my english

Christina.