HELP! :) make a grid circle formula?

hey all,

problem:

i have a grid from 11 x 11 movieclips = 121 movieclips, the first one at _x=0, _y=0 is number 1! etc

now i want to start from the center of the grid movieclips that is number 61 and want to calculate from that 61 a circle movement till i reach the last outside movieclip number 11?

assuming i start from rigth direction:
so i start with number 61,62,73,72,71,61,49,51,51 = a mini grid of 9x9 then i must start from 63,64 till i have a grid of 5x5 including the mini grid…

where can i find a formula calculation!? or help

i hope this makes sense? :))