//this function checks if there are any characters in 'strCheck', that are not in 'strValid'
function fIsTelephoneValidChars(strCheck, strAdditionalChars) {
	var strChar = "";
	var strValid = "0123456789 +" + strAdditionalChars;
	for (var intCount = 0; intCount < strCheck.length; intCount++) {
		strChar = strCheck.charAt(intCount);
		if (strValid.indexOf(strChar) == -1) 
			return intCount;
	}

	return -1;
}