Both of these things require a custom calculation. For the division script you can use something like this:
var a = Number(this.getField("Field A").value); var b = Number(this.getField("Field B").value); if (b==0) event.value = ""; else event.value = a/b;
For the conditional script you can use this:
var a = this.getField("Cell_1A").valueAsString; var b = this.getField("Cell_1B").valueAsString; if (a=="") event.value = ""; else event.value = Number(a)+Number(b);
Thank you for the solution. It solved my problem.