Call for shipping quote?

I've about got the shipping tables set up except for one thing. Our shipping is very simple, we ship everything using U.S.P.S. Priority flat rate envelopes and boxes; of our products (books and brochures), the envelope will hold about 3.25 lb. and the box will hold up to 12 lb. U.S.P.S. has nice flat rates per container, regardless of weight; we use the weight to determine the container for the small orders which are over 95% of our business.

This is all set up - not tested yet :P - and it even has a third level at 99 lb. with a much larger shipping charge. What we'd like to do, though, is tell the customer to email us for a quote on large quantity orders and on international orders (we get a small number of each). Is there any way to make the shipping estimator display "email us for quote"?? Our verbal shipping instructions say this but I'd like to say it in both places as I'm skeptical of people actually reading instructions.

I need to know this too because i have a number of items that are fixed prices but the White Glove delivery options will differ depending on location.

Does anyone have any idea?

I want to be able to set up flat rate at two different prices as well (priority env and box).