For our Magento 18.104.22.168 website we use 2 shipping methods:
- Pickup at store
- Table rate shipping
When the order weight is more than 250kg we want to give a warning at the checkout - shipping process that the customer should ask for a quote. Than the customer can click on the message and a new window shows up with the default Contact page. The customer is still able to check out but will pay 0,00 for shipping. When we made a quote the customer can pay the rest of the shipping costs.
So it's simple;
A simple sentence 'Warning, order weight too high to give a price. Please ask for a quote.' shows up if the order weight is higher than 250kgs and the customer selects 'Table Rate shipping' in the checkout process.