I need to look at a condition and then display from choices which have a weightage.

Example: if (cell A = "yes", "yes", choice)

where choice is either N or NO. N and NO should be picked 20%, 80% of the times respectively.

I tried with rand like this

if (cell A = "yes", "yes", if(rand()<0.2,"N", "NO"))

But I see this changing every time there is a change in the sheet. In my case there are going to be tons of changes. I can use paste special and get away but I was wondering if there is any other option available in excel.

Thanks for the help.