Season Snow contract and question about triggers

[Frag]

Hi guys,

I have that idea in my mind for a while and I am looking for a way to generate revenu while removing snow with a snowblower.

Let's say I would like to generate 0.01$ (as an example) for every litres of snow that pass thru your snow blower, what is trigger/code area I should look at. I know that the snow amount is calculated since I noticed that it is possible to snowblow it directly in a trailer, therefore seeing the exact quantity removed.

Then end goal would be to find a way to write a "Snow blowing contract" mod.

Any hint?