Thanks for the response again Jason. That sounds good alright. There might be a possibility there could be more than 3 ranges but I think it should be ok to tell my client that we need to decide on a fixed number.
I was getting errors in my code when I tried your earlier example. Unfortunately I haven't really had a chance to try debug it yet and anyway I was kind of waiting for your next response.
I will try your latest suggestion and see how I get on.