How to update a field by fetching data from other entity by passing 2 keys

Hi Folks, 

Please advice me in a current scenario--

In a form Inquiry (custom Entity)

I have fields- Products ,Region ,ShppingLocation
Also - Product and Region are separate Entity which is linked with Inquiry Entity.

Now I have one more entity - ShippingEntity 
Which have fields - Products,Region ,ShippingPoint
Data --     Products      Region      ShippingPoint
                   Pen            Asia                    China
                   Mobile      Asia                     China
                  TV              Asia                      Seoul
                  Aircaft       Europe                  Paris
                 Camera      North America      USA

Now In Inquiry Form --
When Inquiry Is created its contains some field along with Product eg - Pen , Mobile, TV but Region is always remains blank.
Now if any one select Region of Inquiry entity (which will be a optional filed) then automatic  Shipping location  should get set in this Inquiry location 

So if In Inquiry if Product set to - Mobile
and Region selected is Asia then Shipping location should set -- China     ------ And this information we need to fetch from  ShippingEntity

So we if we pass two key Product and Region to this entity then we can get its  ShippingPoint 

How I can achive this ? Can I go for javsacript or any other way to do ?

Thanks