Selection and cuts on intermediate particles

Dear Madanalysis team,

I am now studying with MG5 the production of the heavy neutrino N in the process:

p p > w+ > e+ n1

and I'm intersted in computing the forward-backward asymmetry for the w+ decay. For computing this asymmetry I would need to be able to select (or reject) in MA5, the events with rapidity "y" for the intermediate W+ boson, e.g.

select Y(w+) > 0,
...

but MA5 is just considering the final particles in the event record so I'm am not able at the moment to apply any cut on the intermediate particle, the W boson. Is there any way to apply cuts in the intermediate particles?.

I was reading the manual and find information about how to plot the kinematical variables for all the particles in the event record.

Any help or suggestion with this issue would be appreciated.

Thank you.