[Seaside] How do I call a method from renderContentOn:

[ld]

I'm new to Seaside.  It seems very powerful, if I could just understand
it better. I have worked through the tutorial, and thought I'd practice
by modifying the WACounter example to change the change 'interval' from
the browser..  I added a 'interval' variable.  Then added a
selectFromList to  'renderContentOn:' to  quickly change the interval
that the counter is incremented/decremented by.

renderContentOn: html
    html heading: count.
    html anchorWithAction: [self increment] text: '++'.
    html space.
    html anchorWithAction: [self decrement] text: '--'.
    html break.
    html horizontalRule.
    html text:  'Change the interval'.
    html paragraph.
    html form: [
            html selectFromList: (1 to: 10) selected: interval callback:
[:i | interval _ i].
            html submitButton.
        ].
    html text: 'how do I call the setInterval from here?'.
-------
Next,  factored the form into a setInterval method:

setInterval: html
    html text: interval.
    html space.
    html space.
    html form: [
            html selectFromList: (1 to: 10) selected: interval callback:
[:i | interval _ i].
            html submitButton.
        ]
-------
My questions are:
1)  Is my factoring correct?

2)  How do I call this from  'renderContentOn:'  ?

Thanks for you patience with such simple questions.

- Larry Kelly