volvo l 180 third valve install

I have a volvo L180 wheel loader. If i read the spec sheet right all of the loaders come with a 3 spool hydraulic valve. Does anyone know what is involved in setting up the 3rd spool to operate? I have lift and bucket curl and dump on the first two levers. I would like to setup the 3rd valve to run a sweeper attachment for cleaning trailer tops. Any input? I was wondering if volvo sells a kit with everything you need or if you have to buy things a piece at a time?

thanks!