how to make text box dynamic

[vijaypalmanit-1]

I have a dimension product_name, and my requirement is that in dashboard I want to show user with the text: “Hello ABC, this month your most sold product is XYZ”.

I am able to achieve text: “Hello, ABC” in a tile by using dummy dimension, how can I do the same in text box component (is this even possible that we can add some dimension in text box ?):

Second thing is that How to find most sold product using LookML so that I can add that into my text box, I know that using SQL I can achieve this but how to implement same using LookML.