Hi Steve Bosher,
You can design your page with data-grid inside the data-view, if possible relate your data-grid entity with an association to the data-view entity. Configure the datasource of your data-grid with xpath or an association.
So whenever you select the dropdown value of your data-view object in the onChange microflow do an association update based on your need and refresh the data-view object.
Hope this works for you, Thanks!
Do you also refresh your page parameter? You should refresh the object of the dataview that contains the datagrid. Maybe you can put the datagrid inside the dataview that contains the dropdown and refresh the object of that dataview? This will trigger the datasource of the datagrid again.
Not sure if this would work but could you try closing and opening the page again in the miroflow