Different shipping costs for products shipped from 2 dispatches.

[mmponline]

Please help! 
I have a virtuemart cart with products shipped from different dispatches (venues).  Some products are in South Africa, others in US.  When the user buys the product, the cost for the shipping should be determined on where he resides and from where the product will be sent.   Is there a plugin or existing way to do this type of shipping calculations?