Make a second drop down required if the first drop down matches a specific value?

Question

I have a column that in every cell there is a expanded list of names.
If a certain value, for example,

Mario

is selected from the list, then require entry of the values available in the drop down in the second column. If a different value is in the first drop down, then the second drop down is not required.

Answer 1

You could use data validation. In B1, choose data validation, make Allow: a List, and put a formula in Source: that fits your needs.

For example, this formula would allow only a value that you put in column C to be chosen if "Mario" is in A1. Otherwise you can only choose a value in column D.

=IF(A1="Mario",C:C,D:D)

This allows control of your second drop-down.