Fsolve, function, and adding parameters to a script outside of a function help

So I have my function here

 function fcns = CSTReqs(w)
S = w(1);
X = w(2);
CIBAP = w(3);
CIBPE = w(4);
CH2O = w(5);
t = w(6);
Ccat = 0.78;
k1 = 1.14;
k2 = 0.095;
KIBAP = 76.4;
KH2 = 141;
KH2O = 529;
PH2 = 40;
r1 = Ccat*k1*CIBAP*PH2/(1 + KIBAP*CIBAP + (KH2*PH2)^(1/2) + KH2O*CH2O)^2;
r2 = Ccat*k2*CIBPE*PH2/(1 + KIBAP*CIBAP + (KH2*PH2)^(1/2) + KH2O*CH2O)^2;
CIBAP0=5.4;
fcns(1) = CIBAP0 - CIBAP - t*r1;
fcns(2) = -CIBPE + t*(r1 - r2);
fcns(3) = -CH2O + t*r2;
fcns(4) = S - (CIBPE/(CIBAP0-CIBAP));
fcns(5) = X - ((CIBAP0-CIBAP)/5.4);
end

And I want to solve this function by inputting X values ranging from 0 to 1 to see how all of my variables change. Ultimately I want to make a plot of X vs S.

 for X=0:0.1:1
f = @(x) CSTReqs(S,X,CIBAP,CIBPE,CH2O,t);
fsolve(f,[1,1,1,1,1,1])
end

If I input an X into the function itself and use fsolve(@CSTReqs,[1,1,1,1,1,1]), I get a solution. However when I write the code above for changing X values I get

??? Undefined function or variable 'S'.

 Error in ==> @(X)CSTReqs(S,X,CIBAP,CIBPE,CH2O,t)

 Error in ==> fsolve at 248
            fuser = feval(funfcn{3},x,varargin{:});

 Error in ==> CSTR_solved at 3
 fsolve(f,[1,1,1,1,1,1])
 Caused by:
    Failure in initial user-supplied objective function evaluation. FSOLVE     cannot continue.