Pass query to another formDataSource

Good evening developers,

I have a form where I have two instances of salesLine as datasources. Both are attached to grids and the plan is that the first salesLine instance is grouped by itemId. When ever the selection on the grouped salesLine grid changes, the grid with the second instance of salesLine should display only the sales lines that have that itemId. I need to have both salesLine datasources use the same filter criteria outside of the itemId. To do this, I tried this in the ExecuteQuery method of the second datasource. Unfortunately, nothing happens.

What am I missing in this code?