In a relationship table, is it ok to use two foreign key of a combination ID to connect to each other?

[Spidey]

Hi,

I am trying to get the cost from a matrix table. My question is that is it ok to use combine ID using other table ID and use it as a link to connect to other table and get the cost from the matrix, instead of using primary key?  Like using a combination of foreign id key to make one unique key to connect to other table with the same key to get the data.   Is that ok?

If it is not conventional, what is a better proposal?  Many Thanks. 

 

 

Text Matrix.fmp12

Edited June 16, 2020 by Spidey