如何在WrapPanel中的鼠标单击点添加控件

I have a WrapPanel in my program that some button add to it in runtime (like the panel for add tags for question in this site). now I want to click between the buttons and add a new button in the place mouse is clicked.but I don't know how can I get mouse position between button or how to get child index of the button that placed before mouse click! in my program that some butt