Deposition rate using particle tracing module

Hi
I have modeled a reactor using the "fluid flow" and "particle tracing module". A substrate wafer is placed across the flow channel. I have implemented the boundary condition so that whenever a particle hits the wafer, it get stick/freeze with the wafer wall.
Now, If I want to calculate how many particles are stick with the wafer wall and rate of deposition from the result section, how I am supposed to do that?

Thank you.
Rokib