On user input for a drop down only processes once?

On user input for a drop down only processes once?

Hi,
I have a  form with a drop down list. What I wanted to do is each time the user selects a different value from the drop down list to update another field.
That works to update a text-field
(So when I select sometging from the drop down I place the contents of the selected value in the text-field.)

But I also try to update a Note (containing some information about the choice) And that only is updated the first time a user selects an item from the drop down list.
Each time the user selects another value the text field is updated but the Note-field is not.
Is this a bug or is it designed this?
Or am I overlooking something?
Rob