Need help getting information from RadioButton control...

Hi, 

Please see my code below.  How can I set the selectedFeeID value (line 11)?  The value comes from an asp:RadioButton control (line 139).  The code as written give an error at line 11 stating "object reference not set to an instance of an object.  The complication comes from the layers of controls I've nested in the web form.  The nesting looks like this:

1.  ListView1 (lvCourseListing)

  2. ListView2 (lvCourseSections)

          LinkButton (lbAddToCart) -- This causes lbAddToCart_Click to fire, which runs the code below.

    3. ListView3 (lvCourseFeesGroup)

           RadioButton (rdoEnrollmentOptions) -- This has the value I'm trying to set.
1 protected void lbAddToCart_Cl ...