Hi Matt
Thanks for posting in the community! Unfortunately what you are trying to do is not currently supported in Lucidchart. However we're always looking for ways to improve Lucidchart and your feedback is the best way for us to do that. Would you mind adding your idea to our feature request form? Ideas submitted to this form are passed on to the product development team for their consideration.
As a growing company we take our feature requests very seriously. We are continuously looking for how we can make our product more useful and effective for our users and we pass that information directly to our product development team. Feel free to take a look at our Formulas article as a resource about intended functionality of formulas; please let me know if you have any further questions about this!