How to write a formula if () + drop-down list?

Question

Google Sheets

There is a cell with a drop-down list in the table, in this cell I want to write a formula with the IF ( ) operator, but so that it is possible to select from the drop-down list if the conditions of the operator are not met, how can this be done?

Answer 1

Right click on a cell: Data Validation .
Rules: Values ​​from the list
and write all your options there, separated by commas, for example:
=C1-B1,=C2-B2,=C3-B3
Demo table

Answer 2

I think that this is possible only for dependent lists, which are implemented in Tables through all sorts of tricks or scripts and tricks.

• https://www.youtube.com/watch?v=YfVQ_udH7O4
  
• https://www.youtube.com/watch?v=nhsl_iJbn40