function IsInteger(field) {	
    var valid = "0123456789"
    var ok = "yes";
    var temp;
    for (var i=0; i<field.value.length; i++) {
        temp = "" + field.value.substring(i, i+1);
        if (valid.indexOf(temp) == "-1") { ok = "no" };
    }    
    return (ok != "no");
}