Calculate Angle From X, Y Coordinates

I have a userform, on it is a very large command button with a picture of a map loaded on the button. The button is 500 width(X) by 500 height (Y), so the center of the button would be at the location 250 (X) by 250 (Y). The button is coded for mousemove to get the X,Y cooridates and when you _Click the button a textbox gives the distance to the point(mousemove) from the center of the button. All that is good, but now I'd like to find the degree of the point referenced to a compass, ie, if the point is at 250 (X) and (Y) is less than 250 then the point would be due north at 0/360 degrees and if the point (Y) is greater than 250, it would be south of the center of the button. I hope this make sense. It's been a long time since trig. I've been searching but can't seem to find the correct formula to figure this out.

Here's the other problem, I'm doing this in powerpoint so I'm not sure if cos or tan functions are loaded in this program. I am posting this in the xl forum because I figure that's where most of the people who could figure this out are. If this is in the incorrect forum I can try to move it,