Excel - if and or function

The formula I'm trying to write is

CellA             CellB              CellC
Total Price       Order status       开发者_如何转开发Delivery Status**
Null              Authorised    
Null              Authorised         Null
$100              Authorised         Authorised

if cell A = Null and cell C = Null or blank... then "ERROR"

How would I write the formula?

Assuming CellA is A2 and CellC is C2, use this formula below

=IF(AND($A2="null",OR($C2="NULL",$C2="")),"ERROR","NoError")

if you have assigned variable name to each cell you can use CellA and CellC instead

Off the top of my head...

=IF(A2 == "NULL", IF(OR(C2 == "NULL", C2 == ""), "ERROR", ""), "")