Here's what I have:

D4 = Date Companint Received
E4 = Date Complaint Filed
F4 = Networkdays(D4,E4)-1

This works great for what I need, provided that the information in cells D#
and E# are filled out. This sheet that I have is new and a lot of the cells
have yet to be filled in.

The cells where D and E are both blank, F shows -1.
The cells where D is blank and E is valued show a value around 2800
The cells where D is valued and E is blank show a value of around -2800

My question is how can I change the networkdays formula to also meet the
below criteria. I know it will be a nested if, but I'm weak with those.

If D4 = blank and E4 = nonblank - "ENTER DATE COMPLAINT RECEIVED"
If E4 = blank and D4 = nonblank - "ENTER FC FILED DATE"
If D4 & E4 = blank - "FILL IN DATES"
If D4 & E4 are both valued - Networkdays(D4,E4)-1

Thanks in advance