SELECT() not allowing to compare (=) between same data type

[Gigi12]

Hi!
I've been trying to sum all rows from an specific view. 
I believe the formula should be like this SUM (SELECT(QA[Weight],[_THISROW].[Form_Name] = QA[Form_Name])). Selecting rows where the form_name of my current view (forms - form name as key) equals form_name in QA (it's like a details view); however I keep getting an error of "Cannot compared List to Text". Both columns have a Type Text and if I use an IN([_THISROW].[Form_Name], QA[Form_Name]) the select sums all records, not the ones from the form. 

I'm not sure what I'm doing wrong.