How to filter multi select lookup

I am using this add-on for the multi-select functionality: Multi-select text field setup for Creatio

Now I want to filter this multi select field by another lookup on the same page. This works fine when I'm using regular lookups and a business rule.

I tried to modify the example in the documentation by changing "Name" to the correct column name in my multi select lookup. Then i changed "Customer" to this.get(UsrLookup2). 

When lookup2 is filled in on my page and I then open the multi select one, I get no options to choose from in the selection box.

Does anyone know what I should change?

"filters": function() {
return Terrasoft.createColumnFilterWithParameter(
Terrasoft.ComparisonType.EQUAL,
"Name",
"Customer");
},