Radio Buttons in Interactive form

Hi,

I designed a interactive form with two radio buttons(RB) and two subforms(SF).

When I click on RB1,need to display SF1 and when I Select RB2, need to display SF2.

How can I do this.

I wrote a sample code at Clcik even of RadioButtonList

var radioButtons = document.getElementsByName("RadioButtonList");
for (var x = 0; x < radioButtons.length; x++ ) 
    {
        if (radioButtons[1].checked) 
          {
          Subform1.presence = "visible";
        }
        if (radioButtons[2].checked) 
          {
          Subform2.presence = "visible";
        }
      }

But the above code is not working...not triggering anything.

Kindly let me know wat might bthe problem

Regards,

Venkat