function changeProductvc(_this) {
    var pay_link_x = _this.value;
    document.getElementById("pay_link_1").href = document.getElementById(pay_link_x).href;
    if (pay_link_x == 'pay_link_2') {
	document.getElementById("div_download_link_1").style.display = "block";
	document.getElementById("div_download_link_2").style.display = "none";
	document.getElementById("div_download_link_3").style.display = "none";
	}
    if (pay_link_x == 'pay_link_3') 
	{
	document.getElementById("div_download_link_1").style.display = "none";
	document.getElementById("div_download_link_2").style.display = "block";
	document.getElementById("div_download_link_3").style.display = "none";
	}
	if (pay_link_x == 'pay_link_4') {
	document.getElementById("div_download_link_1").style.display = "none";
	document.getElementById("div_download_link_2").style.display = "none";
	document.getElementById("div_download_link_3").style.display = "block";
	}
}