I want to fill a field called "Artists" (string) based on every-time I update a lookup field called "Artist_Name".

So far I've tried several things similar to this:

For every artist in Artist_Name{

Fetchartistname = Artist_Name [ID == input.Artist_Name_Lookup]

input.Artists = Fetchartistname.Name; 

}

All I've been getting is my Artists (string) field being populated with the same name no matter what name is chosen in the multi-select lookup field. 

For instance:

The lookup field has "Judas Priest"

but the Artist string field will be populated with "Justin Bieber" 

The lookup field has "The Eagles"

but the Artist string field will be populated with "Justin Bieber"

Obviously, I don't want Justin Bieber taking over my whole program.

Any help would be appreciated, thanks!