Software to determine how much force is needed for a robotic arm to clean a window

Hi,
I am working on building a robotic arm that would be used to clean windows. I am trying to figure out what software I could use to determine how much force I need to be able to clean the windows. I would appreciate any help or guidance!

Hello Cristian - Seems to me your arm will tell you what load is required... Use a luggage scale and window and there you go. Peter