Question: Extracting information from a procedure?

Hi all,

I am after some advice on how to extract a value from a proc.

iter := proc(f,I1,I2,N,z)         local a,k,:
>                x0 := I1:
>                x1 := I2:
>                   for k to N do
>                        xo := evalf(x0-f(x0)*((x0-x1)/(f(x0)-f(x1))):                 
>                        a[s] := a[s],a[0]:
>                          print(abs(a[s+1]-a[s])):
>                           if z>abs(a[k]-a[k-1]) and k<=N then
>                          print(abs(a[s+1]-a[s])):
>                       end if:
>                    end do:
> end proc:

in the above f is a function, I1 and I2 are initial values, N is an integer, and z is real. xo describes an iteration. I am trying to find the first iterate for which z>abs(a[k]-a[k-1]) and k<=N, and output this to see if the function converges.

i know the xo part works ok, but i am having trouble extracting the above information.

any help appreciated

slip