I created a table to convert between currencies which have a field called "conversão" with a enumeration to each currency:

DE = Dólar to Euro; DK = Dólar to Kwanza; ED= Euro to Dólar; EK= Euro to Kwanza; KD= Kwanza to Dólar; KE = Kwanza to Euro

Then I choose the currencies and set the exchange of the day. It's working fine until here

But what I need is in another table, get an specific value, that is:

Select separately the "valor" from each "conversão" (DE, DK,EK,etc..) so I can add in another table a calculation that will be:

This specific value (the VALUE from Dólar x Kwanza, for example) and multiply another field from another table.
And very important, it must be the LAST value added in table "cambio"

This is my exchange("CAMBIO") table. I'm trying to get the VALOR from an enumeration with value "DK":

So then I can multiply for the value I want but It's not working.
Actually I tried other ways but without success