Hey all

I'm sure this question has been asked a few times before ;o).
Basically I'm looking for a validation rule for the below.
I have a row of data, say A1,B1,C1,D1 where a1 can have either value or used
or Inuse. When the user selects 'Unused' from the dropdown, they will
be forced to enter in details in to the other cells. I.e Name, Department,
Cost Center
ect...

I've tried an IF statement but not being technical this has me stumped.
Any help provided would be a godsend.

Much thanks!
Mel