Running Average

I need to keep a running count of good to bad parts as each part is processed. I came up with the following ladder to keep up with the current quantity of good parts. The bad parts are just the difference from the total parts and the good parts. N7:0 holds the current good part count. N7:0 starts out life with the total count for the Bit Shift so from the git go the math works out correctly. Once the first part is processed if it is good the value in N7:0 remains the same. If the part is bad the value decreses by 1. The value remains at that level unil the bad part passes to the UL bit of the Control for the Bit Shift. The reason is if I get too many bad parts in a row say 10 out of the last 100 I need to shut the machine off and ***** at the operator. Have I missed anything in this logic? Is there a better way?

run of bad parts

what I do for catching a series of bad parts - my customers like to stop after three in a row - is use a counter for the bad part, and reset it with each good part.
Prest the counter with your max number of sequential rejects.
Use the Done bit of the counter to alarm/pause/stop the process.

Average is the way to go. Counter is not good since you might have
an operator does one part ok and next part not. You get an average
of 50% failure which is a huge number. Counter of two is not going to detect it.