Iâ€™m not sure if you intended **Select** data types to work this way or not, but I discovered that you could use a variety of formulas or dates as the select options, and the formulas actually evaluate! This could have some interesting uses, and Iâ€™m only just barely thinking through the implications.

Look at just the following basic example:

You could choose to use the TODAY() formula, or reference cell $J$3 or add 3 days to the date in cell A2 or use the date 5/1/2020. If you manually enter a date, that is automatically added to the select list.

The point is that you actually have a drop down that lets you choose different formulas to use in that cell. That is really cool (and would work even better if the drop-down arrow continued to show up after choosing an option).

In Excel and Google Sheets you either enter a value or a formula. You can create a drop-down list with data validation, but you canâ€™t use formulas in the list. So, what you have done is very interesting.

This would be even more interesting if you could use this within a table with working relative references (so that if you chose the formula, the references could reference values in the current row, or maybe a previous row).

The application where I was trying this out was in a gantt chart where you may want to (1) define the start date as a lookup function (to start the next day after the specified task ID), (2) use WORKDAY to start the next workday after another taskâ€™s end date, (3) choose the Project Start Date cell, (4) add a day to the previous taskâ€™s end date or (5) enter a date manually.

Another more general application of this technique is to use it as a way of preserving the original formula while allowing the user to override the input with a manual number. For example, you might want to allow an invoice number to be entered manually, or selected as the next sequential number from a column of invoice numbers:

Although this is already working, my suggestions for making this a feature rather than a convenient accident would be to make the drop-down arrow still function if youâ€™ve chosen the formula, and to make relative references function correctly within a table as rows are moved or as the formula is copied down.