function jumpField(event, thisField, maxLen, prevField, nextField) {

	code = event.keyCode;

	if((code == 9) || (code == 16)) {
		//don't auto-jump if they're manually tabbing
		return(true);
	}

	if(thisField.value.length == maxLen) {
		if(nextField != '') {
			document.getElementById(nextField).focus();
			document.getElementById(nextField).select();
		}
	}
	else if(code == 8) {
		if(thisField.value.length == 0) {
			if(prevField != '') {
				document.getElementById(prevField).focus();
				document.getElementById(prevField).select();
			}
		}
	}
}