Right, I was thinking in a complete opposite direction for this problem. Here's how you can handle this:
- Go to Manage > Project Parameters > Add and Add a Shared Parameter.
- Create a new SP, Integer, name it something like choose_foundation or something
- Add the SP to Structural Foundations, make it a TYPE parameter
- Add the SP to the project
- Go to the Schedule, add the SP to the Schedule and add values to the different Footing Types, depending on which height column they use (1 for Default Thickness, and 2 for Foundation Thickness). Because this is a type parameter, it will be filled in for all instances (and new instances).
- Create a Calculated Value with this formula: if(choose_foundation = 1, Default Thickness, Foundation Thickness). Now this column will show the thickness.
- Apply this to your template so you never have to do it again...