I am trying to concatenate fields (lookups) from 2 custom modules. But does not seem to work.

    Concat(${Categories.Category Name},' - ',${Manufacturers.Manufacturer Name}

Both Category Name and Manufacturer name are lookup fields in their respective modules.

It works well when I try to concatenate fields from the same module that I am currently in, but provides a syntax error the moment I try to pick a field from another module

Can someone help?