Formula Help - nested statements - different things if cell blank or cell part of formula

Term Date Return Date Comp. Level
7/10/16 7/13/16 higher
3/5/16 7/14/16 lower
4/7/16 7/14/16 lower
7/3/16 7/8/16 higher
1/9/15 7/15/16 lower

I am trying to create a formula that will fill in the Comp Level column based on the following criteria

If return date is blank then Comp. Level is blank
If return date minus term date is less than or equal to 14 then Comp. Level is higher
If return date minus term date is greater than 14 then Comp. Level is lower.

Thanks - that is exactly what I needed