function IsValidFlyBuysNumber(num1,num2,num3,num4)
{
    var valid = true;
    var num1_value = document.getElementById(num1).value;
    var num2_value = document.getElementById(num2).value;
    var num3_value = document.getElementById(num3).value;
    var num4_value = document.getElementById(num4).value;
	
    if (num2_value.length == 4) {
	    if (trimText(num1_value) == '' || trimText(num2_value) == '' || trimText(num3_value) == '' || trimText(num4_value) == '')
	    {   
		valid = false;
	    }
	    else if (num1_value.toString().search(/^[0-9]+$/) != 0 || num2_value.toString().search(/^[0-9]+$/) != 0 || num3_value.toString().search(/^[0-9]+$/) != 0 || num4_value.toString().search(/^[0-9]+$/) != 0)
	    {
		valid = false;
	    }
	    else
	    {
		valid = true;
	    }
	    if (!valid)
	    {
		alert("Please fill in a valid fly buys number.");
	    }
    }
    return valid;
}
function trimText(sString)
{
    while (sString.substring(0,1) == ' ')
    {
        sString = sString.substring(1, sString.length);
    }
    while (sString.substring(sString.length-1, sString.length) == ' ')
    {
        sString = sString.substring(0,sString.length-1);
    }
    return sString;
}