Validation based on contents of another field

[faada]

Hi all, quick question, is it possible to have a "not empty" validation based on the contents of another field?

ie. Field "Reason" should be NotEmpty if field "Sent" has a value of "Not Sent"

[-Queue-]

Validate Reason with Case( Sent = "Not Sent"; not IsEmpty(Reason); 1 ).

If Reason must be empty when Sent <> "Not Sent", then use Sent = "Not Sent" xor IsEmpty(Reason).