Circle Timer

anyone be abel to point me in the right track for making a circular timer?
i have no idea were to start or how i would go about doing this
(id rate myself as medium in AS scripting so dont go to fast)

i want it so that if you feed it 75% it shows up as the 1st image
the second one might be 40% and the last one like 20%
(these are just values i choose to clarify what i want to do :wink:

would be awsome if anyone could make a code snippet for me