How to perform a loop in which values from first leg are taken into second leg?

I have a code which looks like this

%leg 1
a = 0
b = 0
c = 4500
t = 90./60
cend = 4400

%leg 2 
a = 6
b = 55
c = cend
t = 30./60
%leg 3
a = 7.5
b = 80
c = cend 
t = 50./60

%calculation 
(large calculation which includes variables a, b, c & t)

I want to take the precalculated variables from '%leg 1', and plug them into the '%calculation' part of the code. This then returns a value for 'cend', which i then want to take into leg 2, before recalulating the %calculation part of the code with the new values listed in %leg 2. Then i want to repeat this step for %leg 3; altogether I have 9 legs and so I'm rather confused due to the scale of the problem. Is there a way I can create this loop? Thank you!

[David Fletcher]

So, make the 'calculation' a function that takes arguments of a, b,c & t and returns cend - you can call this from whatever 'leg' you want and get cend back from it and do whatever you want with the value.

[Bob Wake]

I'm not sure how I'd go about this? I was convinced I'd need some sort of loop to looked like this;

%leg 1

%calculation (returns value for cend)

%leg 2 (cend from %leg 1 placed here)

%calculation (returns value for cend)

%leg 3 (cend from leg2 placed here)

[David Fletcher]

I'm not saying you don't need a loop (I have no real idea of what you are doing, so I can't really comment, but maybe you want a loop around the 'legs' if the a,b,c,and t parameters are easily calculable from cend). However, the 'calculation' seems to be a common element, takes the same input and returns the same output, so it would make sense to turn it into a function. Maybe (and like I say I have no real idea of what you are doing, so it's only speculaltion on my part), you want something like:

Initialize cend with first value

loop over however many legs you've got

calculate a,b,c & t from cend value ('legs')

call calculation function and get new value for cend

end loop with final cend value