Xcelsius Custom Componet - how to report error message to user

Hello experts:

I have developed an Xcelsius custom component which displays a colorized grid. The grid is a fixed 5 x 5 as per the requirements. It works o.k. I am able to bind th excel data to the grid and drill on a cell.

The only issue I have is if the user binds a larger excel area to my grid. I would like to enforce the requirment that the bound area must be 5 rows and 5 columns only (5 x 5).

Xcelsius reports a pop up message when you attempt to use the toggle button and do not have 2 cells for the source. I would like to display something like this.

I tried an Alert box, but I'm not sure I had it in the right place in the code. I put if in the data setter. This failed utterly.

Any ideas?

Thanks!