Create a validation rule based on another field

Hi There,



I want to set a rule where employees cannot change the "Status" from "Active" to "Closed" if there is no date entered in the "Actual Closure Date" field.



It is probably very simple but I am just confussing myself now, and thats not good at 09:00 aha! Any help is greatly appreciated :)



All the best

Stu :)

Create a validation rule based on another field