Here's what I use when I'm serious about working up a load (this version is set up for evaluating 5-shot groups, but it's easily converted to other group sizes):
It's a bit more labor-intensive, but provides a great deal more information. I like to shoot on those "sighting-in" targets that provide 5 bulls with a 1" grid around them. I shoot the groups using the chronograph and note the velocity for each shot and also make a little drawing so I know which hole corresponds to which shot. That all gets taken home, where I measure the x and y distance from the aiming point for each shot, then enter those two numbers and the velocity for each into the spreadsheet.
The spreadsheet then calculates the center of the group as the mean x and mean y distances and then calculates the distance that each shot is from that group center. Those distances are used to calculate the mean distance from the group center, which is a much better measure of the accuracy (precision, really) of the load than group size, which has lots of drawbacks statistically (though the sheet calculates that as well).
Finally, each shot and the group center is plotted. That all gets printed out and stored in the noteboook. The example I provided represents real data from my .22-250, shot back in September of 2001.