Show Layer within DatField

Hi all,

I am currently building a DataField I would like to "popup" a message when a certain event occurs (e.g. HR > 140).

I was thinking to something like this.

Standard DataField view:

Custom "popup" layer:

Is it doable? If yes, how can I do this? A layer? 
Any code example you can share?

Thank you so much for the support!