For example, you may not be able to choose the state unless you have selected the country first. This construct ensures that you do not miss out on filling some of the data. Something as shown below

A colleague wanted a similar construct in Excel, and the only thing that came to my mind was Data Validation.

How to Restrict Data Entry in a Cell in based on Another Cell

In this tutorial, I will show you how to restrict entries in a cell based on a formula.

Here is how you can create this in Excel

Now when you enter something in cell A2, and if A1 is empty, an error will be displayed.

Quickly Enter Data in Excel in a Specific Order in Non-Contiguous Cells. 10 Excel Data Entry Tips You Can’t Afford to Miss. Creating an Excel Data Entry Form.

So all in all testing LEN 0 is preferable. REgards BRian