There is no array to store it in, nor does it make any sense to store each different value you generate in an array and subtract them, because with one exception (when the value changes from 360 to zero) the value you stored in the textbox will always be 1.
I think you need to go back to your original assignment, and re-read it rather more carefully - what you are asking for does not make any sense at all!
BTW: you can improve this code:
A++;
if ( A == 360 )
{
A = 0;
}
To a single line:
A = ++A % 360;