how to create a new cell attribute and add adorner to the cell

Hi

I am relatively new to InDesign and wanted to do the following

I want to add a new boolean attribute to a selected table cell. When this attribute is set, I would want to draw one line vertical and one line across the selected cell ( kind of like a "Plus" sign over the cell). I am wondering how to go about doing this.

PS: I read the snippet snpManipulateTableStyle and can see how to change a cell style using existing attribute (kcellAttrFillColorBoss). However in my case, i want to create a entirely new boolean attribute and based on it being true or false, I would want to draw the adornment on the cell

Any help with this would be greatly appreciated..

thanks!

Sam