I am a total newbie to this, so I'm sorry if this is a stupid question. Couldn't find the answer on search.

I'm building a form with a lot of fields, that need to be selectively enabled based on the initial selection of a radio button. 

Rather than each radio button's function having a long list of enable/disable actions, I want to have one function that disables all of the fields. Each radio button would then call the function to disable everything, then just enable what fields it needs.

I can't work out how to create this disabling function using the function creator, which doesn't seem to allow functions to interact with form elements (those options are missing from the drag and drop list). When I try to hand-code it (i.e. "disable myTextField;") I'm told that 'disable' is only available as an 'on load' function.

I would be surprised if this is genuinely not possible, so I'm clearly missing something obvious. Can anyone help please?