Help with Networkdays Calculation

[Scoooter]

Dear All

I am currently having problems with the Networkdays calculation in that
my received date is keyed straight away but my due date may remain
blank for sometime. It being blank then throws up a negative number
such as -27887. Is there anyway to have the cell return an "N/a"
if the due date (AN2) is blank?

=NETWORKDAYS(U2,AN2,Holidays!$B$7:$B$14)

Any help would be greatly appreciated.

Thank you
Scoooter

 

[Toppers]

=If(ISBLANK(AN2),"N/A",NETWORKDAYS(U2,AN2,Holidays!$B$7:$B$14)

 

[Scoooter]

=If(ISBLANK(AN2),"N/A",NETWORKDAYS(U2,AN2,Holidays!$B$7:$B$14)