Changing var delay hide amount

This is from a js submenus script and I'm wanting to know how to make it so that it won't disappear until you click another menu.

//Set delay before submenu disappears after mouse moves out of it (in milliseconds)
var delay_hide=500

You don't give much detail, but:-

var tim; // tim must be global

the mouseout function

tim = setTimeout("obj.style.visibility=\'hidden\';",500); // 500 milliseconds delay

the mouseover function

clearTimeout(tim);