i have 3 bounds how to use it ga toolbox can anyone help me??

function [tim]=coolfn(s,n,alp,x) clc clear all s=1.5; alp=0.0827; n=pi; a=(x(1)-x(2)); b=(x(3)-x(2)); r=s^2; y=4/n; z=alp*(n^2); u=(y*(a/b)); tim=(r/z)*log(u);

here x(1),x(2),x(3) are variables. need to put these three bounds into ga toolbox how to implement it help me. thank you