If I got you right, all you wanted to do is to display result set to the user. Have a Repeat Grid with visibility condition set using pxResultCount >0 or using the Function lengthofpagelist. Based on the number of records you have in your pagelist, automatically those many rows will be visible in the grid at runtime when the user gets to this screen.
Is the grid layout referencing a pagelist on the clipboard?
If so then you should just be able to add a page (i.e. a row in the grid) to the pagelist via an activity using a property-set method and set values for your page list on new appended page e.g. myPageList(<APPEND>).pyLabel, or call a data transform which has standard actions APPEND or APPEND AND MAP.