Loop For A Dynamically Generated Form

Here is the code:

function selectDefaults(buttonGroup){
for (i=0; i < buttonGroup.length; i++) {

if (buttonGroup[i].checked == true) {
for (count=1;count < document.addForm.recordCount.value; count++) {
var doc = document.addForm.feature1[i]
var featureVal = doc.value;
featureVal = featureVal.substring(0,2);
if ( featureVal == "SF"){
doc.checked = true}
} }}}

I need help in the second 'for' loop. Currently it is hard coded to replace the value of document.addForm.feature1 - but this field name is dynamically generated via the page it resides within. That being said, its name/id will increment depending on how large the recordset is. i.e. feature2, feature3, feature4 etc....

How do I get this to work in the javascript? I need to use this script to search all the 'feature#' fields in the form when the script is triggered. All I could think of was this: var doc = document.addForm.feature+count+[i]
which gives me a syntax error.

The purpose of this script, for those who will wish to know, is to automatically select all the features of the product that have the text "SF" (standard feature) in their value.