Is it possible to get an equivalent of Excel's "networkdays" function working as a custom calc script in PDFs? I know there's a JS function that's roughly equivalent ("calc.networkdays"). So I figured a script below would work but apparently not.
var DF1 = this.GetField("DateFrom_1").value;
var DT1 = this.GetField("DateTo_1").value;
event.value = calc.networkdays(DF1,DT1);
There's no built-in function in JS that does that. You'll need to write it yourself (or find it, or have someone write it for you).
I've developed code that does similar things in the past. It's not a very simple task, especially not if you want to include holidays in the calculation as well.