function isString(x) { return (typeof x == 'string'); }

function isNumeric(sText)
{
	var ValidChars = "0123456789.";
	var IsNumber=true;
	var Char;

	for (i = 0; i < sText.length && IsNumber == true; i++) 
	{
		Char = sText.charAt(i); 
		if (ValidChars.indexOf(Char) == -1) 
		{
			IsNumber = false;
		}
	}

	return IsNumber;
}