function updateNumbers()
{
	AtoH = new Array('ANY', '1', '2', '3', '4', '5', '6', '7', '8', '9', '10', '11', '12', '13', '14', '15', '16', '17', '18', '19', '20');
	JtoR = new Array('ANY', '1', '2', '3', '4', '5', '6', '7', '8', '9', '10', '11', '12', '13', '14', '15', '16', '17', '18', '19', '20', '22', '30', '33', '40', '44', '50', '55', '60', '66', '70', '77', '80', '88', '90', '99', '100', '111', '200', '222', '300', '333', '400', '444', '500', '555', '600', '666', '700', '777', '800', '888', '900', '999');
	KandM = new Array('ANY', '1', '2', '3', '4', '5', '6', '7', '8', '9', '10', '11', '12', '13', '14', '15', '16', '17', '18', '19', '20', '22', '30', '33', '40', '44', '50', '55', '60', '66', '70', '77', '80', '88', '90', '99', '100', '111', '155', '200', '222', '300', '333', '400', '444', '500', '555', '600', '666', '700', '777', '800', '888', '900', '999');
	StoY = new Array('ANY', '1', '2', '3', '4', '5', '6', '7', '8', '9', '10', '11', '12', '13', '14', '15', '16', '17', '18', '19', '20', '21', '22', '23', '24', '25', '26', '27', '28', '29', '30', '31', '33', '40', '44', '50', '55', '60', '66', '70', '77', '80', '88', '90', '99', '100', '111', '121', '123', '200', '222', '300', '321', '333', '400', '444', '500', '555', '600', '666', '700', '777', '800', '888', '900', '999');

	with(document.form.regnums)
	{
		selectedPrefix = document.form.Prefix[form.Prefix.selectedIndex].value;

		for(i = options.length - 1; i >= 0; i--)
		{
			options[i] = null;
		}

		switch(selectedPrefix)
		{
			case '': case 'A': case 'B': case 'C': case 'D': case 'E': case 'F': case 'G': case 'H':
				for(i = 0; i < AtoH.length; i++)
				{
					options[options.length] = new Option(AtoH[i], AtoH[i]);
				}
			break;
			case 'J': case 'L': case 'N': case 'P': case 'R':
				for(i = 0; i < JtoR.length; i++)
				{
					options[options.length] = new Option(JtoR[i], JtoR[i]);
				}
			break;
			case 'K': case 'M':
				for(i = 0; i < KandM.length; i++)
				{
					options[options.length] = new Option(KandM[i], KandM[i]);
				}
			break;
			case 'S': case 'T': case 'V': case 'W': case 'X': case 'Y':
				for(i = 0; i < StoY.length; i++)
				{
					options[options.length] = new Option(StoY[i], StoY[i]);
				}
			break;
		}
	}
}

function isNumeric(number)
{
	var strValidChars = "0123456789.-";
	var strChar;
	var valid = true;
	if (number.length == 0) return false;
	for (i = 0; i < number.length && valid == true; i++)
	{
		strChar = number.charAt(i);
		if (strValidChars.indexOf(strChar) == -1)
		{
			valid = false;
		}
	}
	return valid;
}

function isAlpha(alphas, type)
{
	if(type == 'prefix')
	{
		var strValidChars = "ABCDEFGHJKLMNOPRSTUVWXY";
	}
	else
	{
		var strValidChars = "ABCDEFGHJKLMNOPRSTUVWXYZ";	
	}
	var strChar;
	var char = 0;
	var valid = true;
	for (i = 0; i < alphas.length && valid == true; i++)
	{
		strChar = alphas.charAt(i);
		if (strValidChars.indexOf(strChar) == -1)
		{
			char = i + 1;
			valid = false;
		}
	}
	return char;
}

function updateNumberPrefix(number)
{
	if (isNumeric(number) == false)
	{
		number = '';
	}	
	if(number.length == 0)
	{
		document.images.prefix_number_1.src = 'http://www.make-your-own.co.uk/images/plates/any_number.gif';
		document.images.prefix_number_1.width = 27;
		document.images.prefix_number_2.src = 'http://www.make-your-own.co.uk/images/plates/any_number.gif';
		document.images.prefix_number_2.width = 27;
		document.images.prefix_number_3.src = 'http://www.make-your-own.co.uk/images/plates/any_number.gif';
		document.images.prefix_number_3.width = 27;
	}
	if(number.length == 1)
	{
		document.images.prefix_number_1.src = 'images/plates/' + number.charAt(0) + '.gif';
		if(number.charAt(0) == 1)
		{
			document.images.prefix_number_1.width = 11;
		}
		else
		{
			document.images.prefix_number_1.width = 27;
		}
		document.images.prefix_number_2.src = 'http://www.make-your-own.co.uk/images/spacer.gif';
		document.images.prefix_number_2.width = 0;
		document.images.prefix_number_3.src = 'http://www.make-your-own.co.uk/images/spacer.gif';
		document.images.prefix_number_3.width = 0;
	}
	if(number.length == 2)
	{
		document.images.prefix_number_1.src = 'http://www.make-your-own.co.uk/images/plates/' + number.charAt(0) + '.gif';
		if(number.charAt(0) == 1)
		{
			document.images.prefix_number_1.width = 11;
		}
		else
		{
			document.images.prefix_number_1.width = 27;
		}
		document.images.prefix_number_2.src = 'http://www.make-your-own.co.uk/images/plates/' + number.charAt(1) + '.gif';
		if(number.charAt(1) == 1)
		{
			document.images.prefix_number_2.width = 11;
		}
		else
		{
			document.images.prefix_number_2.width = 27;
		}
		document.images.prefix_number_3.src = 'http://www.make-your-own.co.uk/images/spacer.gif';
		document.images.prefix_number_3.width = 0;
	}
	if(number.length == 3)
	{
		document.images.prefix_number_1.src = 'http://www.make-your-own.co.uk/images/plates/' + number.charAt(0) + '.gif';
		if(number.charAt(0) == 1)
		{
			document.images.prefix_number_1.width = 11;
		}
		else
		{
			document.images.prefix_number_1.width = 27;
		}
		document.images.prefix_number_2.src = 'http://www.make-your-own.co.uk/images/plates/' + number.charAt(1) + '.gif';
		if(number.charAt(1) == 1)
		{
			document.images.prefix_number_2.width = 11;
		}
		else
		{
			document.images.prefix_number_2.width = 27;
		}
		document.images.prefix_number_3.src = 'http://www.make-your-own.co.uk/images/plates/' + number.charAt(2) + '.gif';
		if(number.charAt(2) == 1)
		{
			document.images.prefix_number_3.width = 11;
		}
		else
		{
			document.images.prefix_number_3.width = 27;
		}
	}
}

function updateNumberCurrent(number)
{
	if(number == '')
	{
		document.images.current_number_1.src = 'http://www.make-your-own.co.uk/images/plates/any_number.gif';
		document.images.current_number_2.src = 'http://www.make-your-own.co.uk/images/plates/any_number.gif';
	}
	else
	{
		document.images.current_number_1.src = 'http://www.make-your-own.co.uk/images/plates/' + number.charAt(0) + '.gif';
		document.images.current_number_2.src = 'http://www.make-your-own.co.uk/images/plates/' + number.charAt(1) + '.gif';
	}
	if(number.charAt(0) == 1)
	{
		document.images.current_number_1.width = 11;
	}
	else
	{
		document.images.current_number_1.width = 27;
	}	
	if(number.charAt(1) == 1)
	{
		document.images.current_number_2.width = 11;
	}
	else
	{
		document.images.current_number_2.width = 27;
	}
}