Calculation - Calculating Difference in Days

[bdav1216]

Attempting to subtract dates using NETWORKDAYS.

=NETWORKDAYS(BN2,O2)
BN2 Value = 07/25/2016
O2 Value = 07/28/2016
Returns Value: 1

Everything seems to be working fine except for the following scenario's:

I have some illogical data that I would like to exclude:
=NETWORKDAYS(BO5,BA5)
BO5: 01/11/2017
BA5: 11/30/16
Returns Value: -31
When I have a negative value, how do I reset that to EITHER
1) an absolute value of 31
OR
2) output a '-1'

I have another situation where BA is empty, but BO has a value of 12/20/2016.
The return value is -30517
Is there a way to return a value of -1 when one of the two values is blank? Otherwise this will skew my results.

[etaf]

you could use an IF statement to test if the values are blank or the result negative and give -1

=IF( OR( BO5 ="" , BA5 = "", NETWORKDAYS(BO5,BA5)<0 ) ,-1, NETWORKDAYS(BO5,BA5))

or if you want -31 to 31 - USE ABS()

=IF( OR( BO5 ="" , BA5 = "" ) ,-1, ABS(NETWORKDAYS(BO5,BA5)))