Since I have worked with 3D rotational grids, I can probably help. This is less complicated, and actually similar to something I just did. I've attached the file as a reference (ignore the blank event I didn't realize they'd both appear), although the grid in this example is not isometric.
If you look where in the list (named fogstatus) that I am looking, it uses the x and y values as text, in the "text + text" block. You will need to use 2 (blue) attributes, and it's probably best to use the scene maker to set them. So then you can think of it like a normal grid, like I do when my grid can be any sort of rotation.
I'd have to think a bit more before I fully have the solution, but this might help you somewhat.