function validateZIP(field) {
		var valid = "0123456789-";
		var hyphencount = 0;
		
		if (field.length!=5 && field.length!=10) {
		alert("Please enter your 5 digit zip code.");
		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 in your zip code.  Please try again.");
		return false;
		}
		if ((hyphencount > 1) || ((field.length==10) && ""+field.charAt(5)!="-")) {
		alert("The hyphen character should be used with a properly formatted 5 digit+four zip code, like '12345-6789'.   Please try again.");
		return false;
		   }
		}
		return true;
}