i have known for a while that i need to tackle this problem, so here i am. i keep track of the expectancy for all of my trades and they are grouped into systems. this way i know how each system is doing. from this i can also use the information to help size my future positions. here is my problem: i don't want to include every single trade i've made in the calculation. as my trading improves, i don't think i should include old bad trades in the calculation. so i'd like to always use only the last, for example, 100 trades. now if i have a column of numbers in excel, how can i have excel only use the most recent 100 numbers? i made a very simplified excel file to help explain the concept. if anyone can help with a solution, thanks.