Sue,
A couple of things. A qualifying index is an index that is reasonably available to the consumer. That is, can the consumer pick up, say, a Wall Street Journal and find the index you select. You don't want to use the price of bread at the local supermarket as your index as it is not reasonably available to everyone (smile). Next contract law comes into play. If it says something to the effect that you may change the index at some future date or if the current index becomes unavailable, you will select another qualifying index which has an historical movement substantially similar to the original index, then ok. However, if the contract does not allow for you to change the index (of course depending on the language), then you have a change in terms issue, which would require customer approval of the change. Lastly, the index cannot be under the creditors' control. It must be independent. Take a peek at Section 226.5(b).