List validation - Multiple Columns

Question

Hopefully this is really simple, but I can't get my mind around it.

At the title suggests, I have a series of column. Towards the end of them there are 3 columns, "Level 2", "Level 3" and "Level 4".

I want to set it so the user cannot set level 3 to yes (those columns are choice and use a drop down of yes or no, default no) if level 2 is no. Or set level 4 to yes if both levels 2 and 3 are no.

I only want it to trigger obviously when they change the default to yes, so new entries don't bug out.

How can I achieve this?

I managed to cobble this together:

=IF(Lvl3="Yes",AND(Lvl2<>"No",AND(Lvl4<>"No")),TRUE) 

This works if I change Lvl3 to yes. But Not level 4.

I then tried this, which didn't work:

=IF(Or(Lvl3="Yes",AND(Lvl2<>"No",AND(Lvl4<>"No")),TRUE, IF(Lvl3="Yes",AND(Lvl2<>"No",AND(Lvl4<>"No")),TRUE))   

Answer 1

You can try the below and let me know.

=IF(OR(AND(Level2="No",Level3="Yes"),AND(AND(Level2="No",Level3="No"),(Level4="Yes"))),FALSE,TRUE)

Valid Entries