Auto refresh external look up field

[ApaliNa1]

How to auto refresh external look up field when related field selection is updated. I have 3 external lookup field, one is fetching investments and another fetching product and the 3rd one fetching applicable currency related to the selected investment and product from a source. when I change the product manually, the currency still displays previous currency value, although there applicable currency on the dropdown. What steps to be followed, so that the currency is auto updated and previous currency value is auto refreshed when product is updated.

[Sven-iX · Accepted solution]

External lookup fields are not connected to each other. Just like a type-ahead field or a dropdown won't change their selection if a previous field changes. 

The {dependency} (in your case product is a dependency for currency) only comes into play when you click the dropdown (ie, it only affects the API). It doesn't retrigger the lookup automagically.