Remove shipping when cart is over a specific value

Hi all

I have been playing with different ecommerce software and am leaning towards opencart as it seems to do everything i could need.

I am using open cart 1.5.1.3

My question is how can you prevent a shipping options showing up when a cart reaches a certian value.

For example in the royal mail extension you can specife seccond class and first class, but the compensation for this type of service is only £46. So if the cart value reaches this amount i would like it so id does not show these as and option.

Any help appreciated.

BUMP

Anyone have any ideas?