Formula to label the points of a polygon.

Hi,

I've got a challenge that only an excel wizard could complete!

Given 5 pairs of x & y coordinates, I need to label the points consistently by formula!

I have determined that point "A" will be the x,y coordinate with an x value closest to the x value of the center of the polygon.

I've attached a worksheet with 5 sets of sample data, all being 5 sided polygons. The polygon's points are in the yellow columns and I need to fill in the Label column with the labels "A", "B", "C", "D" & "E". Please ignore the grey columns. Thanks.

The center x,y coordinate is just the average of the 5 coordinates but what kind of formula would I use to label the other points consistently, preferably clockwise from point "A"?

Any help is appreciated.

Bye