function ForceNumeric(field) {
    var inputStr = field.value.toString();
    var strLength = inputStr.length;
    var newStr = "";

    for (var i = 0; i < strLength; i++) {
        var oneChar = inputStr.charAt(i);

        if (!(isNaN(oneChar) || oneChar == ' ') || oneChar == '.') {
            newStr = String(newStr) + String(field.value.substring(i, i + 1));
        }
    }
    if (newStr != field.value) {
        field.value = newStr;
    }
}

function NumericKeyUp(fieldToEval, fieldToEvalLength, objToJumpTo) {
    ForceNumeric(fieldToEval);
    if ((fieldToEval.value.length == fieldToEvalLength) &&
		(fieldToEval.value != prevValue) && (objToJumpTo != null)) { objToJumpTo.focus() }
    prevValue = fieldToEval.value;
}

function fieldcheck(field, lng, nxtfield) {
    if (field.value.length >= lng) {
        eval('field.form.' + nxtfield + '.focus()'); 	// automatically move cursor to the next phone number field
    }
}