Expanding an equation in Matlab based on user input? Even possible?

Greetings all,

I've been thinking about this all night and I don't even know if it's possible to do in Matlab, but for this question I am referring to page 8 of the following manual (sorry about the length of this question):

 http://www.geonics.com/pdfs/technicalnotes/tn6.pdf

So, I'm coding up the equations in that manual and this is what I have so far:

Response_values_V= 0:0.01:3.5;
R_v=zeros(size(Response_values_V));

Response_values_H= 0:0.01:3.5;
R_h=zeros(size(Response_values_H));

for n=1:length(Response_values_V)
  rValue_V = Response_values_V(n);
    if rValue_V < 3.6
        R_v(n)=1/sqrt(4*rValue_V.^2+1);
    else
        R_v(n)=0;
    end
end

for n=1:length(Response_values_H)
  rValue_H = Response_values_H(n);
    if rValue_H < 3.6
        R_h(n)=sqrt(4*rValue_H.^2+1)-2*rValue_H;
    else
        R_h(n)=0;
    end
end

z1 = input('Enter z1 value = ');
z2 = input('Enter z2 value = ');
sig1 = input('Enter conductivity of the first layer = ');
sig2 = input('Enter conductivity of the second layer = ');
sig3 = input('Enter conductivity of the third layer = ');
z1scaled = z1*100;
z2scaled = z2*100;

sig_a_v = sig1*(1-R_v(z1scaled))+sig2*(R_v(z1scaled)-R_v(z2scaled))+sig3*R_v(z2scaled);
sig_a_h = sig1*(1-R_h(z1scaled))+sig2*(R_h(z1scaled)-R_h(z2scaled))+sig3*R_h(z2scaled);

As you can see I coded up Figure 7 in this pdf and extended the limits to 3.5 (V is for vertical polarization and H is for Horizontal, and the equation for Figure 7 is found on the last page of that pdf), and matched codding up the equation at the bottom on page 8. Granted this is for a 3 layer system with 3 conductivities, and I have user input to define the conductivities as well as the thickness "z" of the layered model as shown in the pdf. I also scaled "z" since I plot (code withheld for brevity) by .01 increments, not 0.1.

Anyway, while this code works only for this example here, what would I need to do in Matlab to change

sig_a_v = sig1*(1-R_v(z1scaled))+sig2*(R_v(z1scaled)-R_v(z2scaled))+sig3*R_v(z2scaled);

on the fly?

Say I have 4 layers and for conductivities, it would have to look something like

sig_a_v = sig1*(1-R_v(z1scaled))+sig2*(R_v(z1scaled)-R_v(z2scaled))+sig3*(R_v(z2scaled)-R_v(z3scaled))+sig4*R_v(z3scaled);

See how I lengthened the equation based on an additional layer? I'm trying to do this for n layers based on user input.

Is this even possible?

Thanks! -J