=if function with networkdays

edited 12/09/19 in Smartsheet Basics

I am attempting to write a formula where I can look at a date field and if it is blank have the formula calculate networkdays between two fields and if the date field is not blank then calculate the networkdays between a different two fields.  

I have this as my formula:

=if([Order Approval Date]2 ="",NETWORKDAYS([OAM Date]2,[Contract Signature Date]1,ELSEif([Order Approval Date]2<1,networkdays([Order Approval Date]2,[Contract Signature Date]1))

Any help is most appreciated.