Yes you can use .Net functions, you need to enabled the advanced mappings in the advanced options dialog and add for example a text filed into your card and define it as script.
When you close the designer and get back into the main interface, select the edit mappings button in the configurations tab and map the previously created text field as .net function, that mapping type will show you the configuration panel to point to your .net file and select the class and function you want to call.
Before loosing time on writing scripts, first consider whether you can achieve the same thing with storage items. Ate least the example you give above seems to be standard storage/item functionality that doesn't require any scripting.
Senior Software Engineer
"A reasonable man adapts himself to the world. The unreasonable man persists in trying to adapt the world to himself. All progress, therefore, depends on the unreasonable man." (Bernard Shaw)