Draw a perfect circle with the circle tool. Make it the proper size.
Under AutoShapes, Block Arrows, is a half-round arrow. Draw one of those.
There's a little yellow grabber that can be moved to adjust the arc of the
arrow. Make it some equal fraction of 360 degrees, such as 180, 90, 60, 45,
etc. (I think you have to ballpark these, or use some externally-made
guide.)
Copy/paste as many more arrows as you need. Rotate the arrows on top of the
perfect circle drawn earlier.
Is this what you're after?
-John O