Custom fields/ attributes

[raunhar]

Is it possible to have attributes / cutom fields like in the example.
http://www.trendy16.com/catalog/product/view/id/24393/s/14sk11039-11503/category/76/

When some one selects Regular Size, then a form shows up. And if the user selects As Per your Size, then another options shows.

[Studio 42]

You can, but i don't know if a plugin exist for this, it's not a core feature.
So this need perhaps a specific development.