Shipping rules (over 50lbs)

Hello everyone.
I have a basic question.

We have over 2000 products for sale, majority of them weights less then 50 lbs.
For theses products that weights over 50lbs, I would like to use the following rule.

If weight > 50 lbs, do not charge for weight, charge only for items in the cart, and ask customer to call the store manager to find out what the shipping costs will be.

Is there a easy way to setup this rule?
Thanks
Alvaro

You need this for when the whole order has a weight of > 50 or when quantity 1 of a Product is > 50 ...

Or, would it be better to have a flag on these products ... such as Call for Price ... where the customer can see everything about the product except purchase them online as they need to "Call for ..." something to complete the order on these products ...

Note: the text and image of products marked as Call for Price can always be changed to meet your particular needs ...