pls correct this simple error? i cant identify at which place trouble on my code

   clear all;
clc;
format short;
random_no=0;
load_array=zeros(1,10);
plp_array=zeros(1,10);
slot=input('Enter the no of slot for Simulation=');
n=input('Enter the no of inputs='); %part of dest assign module
b=input('Enter the size of buffer='); 
fileID = fopen('results1.txt','wt'); ............when i run this code it shows this error
??? Undefined function or method 'dest_fxn' for input arguments of
type 'double'.

Error in ==> e at 23
            des=dest_fxn(n);   
for load=0.1:0.1:1.0
    fprintf(fileID,'\r\nFor load =%f',load); %load varying from 10% to 100%
    packet=0;                   
    tloss=0;
    tload=0;
    clear buffer_fxn_temp;
    for run=1:slot
        A=zeros(1,n);               %initializing output matrix
        for port=1:n
            random_no=rand(1);
            if random_no<load
            packet=packet+1;   
            des=dest_fxn(n);            %calling Function dest_fxn
            A(1,des)=A(1,des)+1;        %part of dest assign module
            end
        end  
    y=buffer_fxn_temp(n,b,A);          %calling function buffer_fxn
    tloss=tloss+y;
    end
    temp_load=uint8(load*10);
    plp=tloss/packet;
    load_array(1,temp_load)=load;
    plp_array(1,temp_load)=plp;
    fprintf(fileID,'\r\nTotal No of packet Loss=%d\r\nSum of all the packets=%d',tloss,packet);
end
 semilogy(load_array,plp_array);
    hold on;
    grid on;
fprintf(fileID,'\n  ********** End **********\n')
fclose(fileID);

[Mischa Kim]

Where and how is dest_fxn defined?