Custom Activity Data Grid / Variable


I’m trying to create a custom activity to call a web service with multiple inputs and outputs. In general it looks ok, i got my inputs, and got result from service, but there are 2 questions.

1- as you can see, i used a datagrid to get multiple inputs from user, but i couldn’t find a way to use variables (i mean uipath studio variables). How can i access a custom variable from my custom activity ?
2- I want to update output grid after running some calculations, is it possible to access variables from designer project ? or is there event that can i use in designer project ? (like an event fired after “ExecuteAsync”)