function validateZIP(field) {
var valid = "bz8y9p";
var hyphencount = 0;

if (field.length!=6 && field.length!=10) {
alert("Please enter the correct 6 characters.");
return false;
}
for (var i=0; i < field.length; i++) {
temp = "" + field.substring(i, i+1);
if (temp == "-") hyphencount++;
if (valid.indexOf(temp) == "-1") {
alert("Invalid characters - please try again.");
return false;
}
if ((hyphencount > 1) || ((field.length==10) && ""+field.charAt(6)!="-")) {
alert("Invalid characters - please try again.");
return false;
   }
}
return true;
}