Hi Niels,
so, the option is a "variable". That's fine, you can use a variable name in place of a
'fixed text' for the radio option in the template settings.
search for where the template is using that variable name (in the value::fieldname) and prime
the variable before then. (you could use, for example, a sessionValue if you liked.)
then, when the user does something that causes the radio to change, refresh the Radio field.
For example, if they click a checkbox, then add the Radio field to the list of "reset fields" for the checkbox.
cheers
Bruce