Setting precise angles on pie and arc shapes

Hello,

I would like to setup a radial progress indicator for my modules which I am building in Storyline 360. It would start blank and slowly fill in to complete a full loop or circle as the learner progresses.

Storyline 360's built-in page numbers should make this a snap to setup but I've hit a snag with the shape properties. The pie and arc shapes both allow you to set the completeness of the circle by dragging the yellow box, but the controls seem to be only visual - there is no way, for example, to enter five degrees on the pie shape to have the pie take up exactly five degrees of the circle. 

Given the name of the software, this seems like a grave oversight. I wonder if anyone has a trick that could get around this limitation? We really have our heart set on a radial progress indicator.

Thanks,

Kevin