Data validation: Restrict cell until another cell has a value, then provide drop down list

Hi all,

I am trying to create a data validation setup that will prevent the user from entering a value in Column A until the corresponding row in Column P has a value. Once this condition is met I would like to allow a selection from a data validation list.

I was able to find a formula to restrict entry on this forum:

=AND(P4<>0,P4<>"")

However I am not certain how to then move to providing for the drop down list. How should I approach this?

Thanks!

Maybe?

You could use formula's for a reminder in A1, for example. In P1 do your dropdown list. In A1
=IF(AND(OR(A1=0,A1=""),P1<>""),"PLEASE ENTER A VALUE IN P1 BEFORE CONTINUING","")

I found that in another post and tried to adapt to your situation. I don't think it's correct.

The original:

You could use formula's for a reminder in C1, for example. In B1 do your dropdown list. In C1
=IF(AND(OR(A1=0,A1=""),B1<>""),"PLEASE ENTER A VALUE IN A1 BEFORE CONTINUING","")


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