function allow_only_digits()
{
    if (window.event.keyCode<48 || window.event.keyCode >57) 
	{
	window.event.keyCode = "0"
	alert("Please enter only digits")
	}
} 

function confirm_quantity(txt_control)
{
    if (txt_control.value=="")
	{
	alert("Please enter a quantity")
	txt_control.focus()
	return true
	}
    else {return false}
}

function is_empty(txt_control,content_name) 
{
    if (txt_control.value=="") 
   	{
	alert(content_name + " is required!")
	txt_control.focus()
	return true
    	}
    else {return false}
}

function is_digital_valid(txt_control,content_name,num_of_digits) 
{
    if (txt_control.value.length!=num_of_digits) {
	alert("Enter " + num_of_digits + " digits of your " + content_name)
	txt_control.focus()
	return true
    }
    else {return false}
}