如果选择了单选按钮选项，则在Total中添加50％的折扣（RSForm！Pro）

I have a RSform!Pro which is working great except for... I need to apply a 50% discount if people select a certain option in a radio button group. I'm using a code that should work as I found it in RSJoomla forum and they say it works. But not for me:I have a RSform!Pro which is working great exce