Help with subs command and symbolic variables

i have written a piece of code,(apologises for it not being that quick or tidy) but the symbolic values between lines 72 and 78 won't substitute in for the prescribed values above?.. and i have no idea what im missing or could be wrong :(

    function assignment_3_5
    clc
    close all
    syms m1p m2p a1p a2p k1 k2 d1p d2p Fp m1q m2q c1 c2 a2q a1q v1q v2q dt F1 Fq
    k1 = 1; k2 = 0.1; c1=0.1; c2=1; 
    m1p = 3; m2p=1.5;
    m1q = 2; m2q=1;
    EQN1=[m1p 0;0 m2p]*[a1p;a2p]+[(k1+k2) -k2; -k2 k2]*[d1p;d2p] -[F1;Fp]

    EQN2=[m1q 0;0 m2q]*[a1q;a2q]+[(c1+c2) -c2; -c2 c2]*[v1q;v2q] -[0;Fq]

    syms diss1q1  diss1q2 veloc1q diss1p1  diss1p2 veloc1p
    a1q = (((diss1q2 - diss1q1)/dt^2)-(veloc1q/dt));
    a1p = (((diss1p2 - diss1p1)/dt^2)-(veloc1p/dt));

    v1q = ((diss1q2 - diss1q1)/dt);

    syms diss2q1  diss2q2 veloc2q diss2p1  diss2p2 veloc2p
    a2q = (((diss2q2 - diss2q1)/dt^2)-(veloc2q/dt));
    a2p = (((diss2p2 - diss2p1)/dt^2)-(veloc2p/dt));

    v2q= ((diss2q2 - diss2q1)/dt);

    d1p = diss1p2;
    d2p = diss2p2;

    EQN1 = subs(EQN1);
    EQN2 = subs(EQN2);

    %p
    eqn1 = EQN1(1,1);
    eqn2 = EQN1(2,1);
    %q
    eqn3 = EQN2(1,1);
    eqn4 = EQN2(2,1);

    %simplify equations 4 sep eqns in for expanded system
    eqn1=simplify(eqn1);
    eqn2=simplify(eqn2);
    eqn3=simplify(eqn3);
    eqn4=simplify(eqn4);
    % 
    %  pretty(eqn1)
    %  pretty(eqn2)
    %  pretty(eqn3)
    %  pretty(eqn4)

    %%%system Q
    %%%solve eqn3 for diss1Q2

    diss1q2 = solve(eqn3,diss1q2);
    Fq = solve(eqn4,Fq);

    Fq = subs(Fq)

    %%%System P
    %%%subs Fq into eqn2 for Fp
    Fp = -Fq;
    disp('System p')

    diss1p2 = solve(eqn1,diss1p2);
    diss2p2 = solve(eqn2,diss2p2);
    diss1p2 = subs(diss1p2)

    DT=linspace(0,50,100);
     %assume known dissplacment of balls 1 and 2
    diss1p1 = 0;diss2p1 = 0;
    diss1q1 = 0;diss2q1 = 0; diss2q2 = 1;
     %assume known velocityies of balls 1 and 2
    veloc1p = 0;veloc2p = 0;
    veloc1q = 0;veloc2q = 0;
    F1=0;
    temp = subs(diss1p2)
    for i = 1:100

        dt = DT(i);
        plt(i) = subs(temp);
        %plt(i) = (-1200 -1860*dt -500*dt^2 - 682*dt^3 - 22*dt^4) / ((11*dt + 20)*(2*dt^4  + 39*dt^2  + 90));

    end

    plot(DT,plt)

    end

[Walter Roberson]

Is it dt that is not being substituted?

Have you tried

plt(i) = double( subs(temp, 'dt', dt) );