|You do not need Conditional Formatting for this, just a formula.|
With your data like this:
A B C
1) Due Date Completion Date Status
2) 03/20/2016 03/23/2016 Delayed Completion
3) 03/20/2016 03/20/2016 Completed
4) 03/20/2016 Not Completed
Put this formula in cell C2 and drag down:
=IF($B2>$A2,"Delayed Completion",IF($B2="","Not Completed","Completed"))
See how that works for you.
Also, Excel questions are best asked in the Office Software forum.
message edited by mmcconaghy