interop detecting linked cell changes

[tecman234]

I have an application that periodically updates cells in excel. These cells are linked to the 'rt' app with formulas like
=rt|ESZ4!LAST

I am trying to detect when these cell values change with a .net C# application. I have setup excel interop, and can detect manual cell changes with the worksheet Change event. However, the Change event does not fire when the 'rt' app updates the cell values.
How can interop detect a value change in one of these linked cells?

thanks.

[romperstomper]

The only direct event would be the Worksheet_Calculate but that can't be restricted to only react to specific cells recalculating.