I don’t know your exact data model and names, but I assume this is a data grid inside the same data view that also holds your reference selector?
Easiest would be not to use the ‘on change’ event of the reference selector, but instead to use a microflow as the data source for the data grid.
The microflow has a retrieves and returns the objects for your data grid from database, with an XPath constraint:
(you’ll need to fill in the right names, but basically you are getting the objects for the data grid, and saying the association with SEGMENT leads to the same segment that the outer data view refers to in the reference selector)
And you also need to make sure the data grid updates, such that changes in the reference selector are reflected: easiest is to set refresh time for the grid: