programming help needed !!!

[ACLerok]

I am supposed to make a program where the user selects a number between 1 and 100 and then the computer will attempt to guess that number. After each guess, the use will enter whether the number was too high or too low. So far i have this,

function guessnum(low,high)

n=floor((high-low)/2);
disp(sprintf('%d',n));
ans = input('High or Low? ','s')

if strcmp(ans,'correct')
disp(sprintf('Computer wins'));

elseif strcmp(ans,'high')
guessnum( ,n);

elseif strcmp(ans,'low')
guessnum(n, );


end

the thing i am having trouble with is what to put with each recursive function call. I know that if the number is too high, return that guess has the upper bound and vice versa with the lower bound. I just don't know how to calculate the lower bound if the guess is too high or the higher bound if the guess is too low. can OT help me out?