can anyone help fix this statement?

var a = this.getField("PREM&LOSS.0.2").value

var b = this.getField("PREM&LOSS.0.1").value

var f = this.getField("PREM&LOSS.0.33333")
f.value = b/a

I'm getting the error "the value entered does not match the format of the field" I was informed I need an if state "As an example, let's assume that we have a simple division c = a/b. In
order to prevent illegal results, we would have to prevent a division
by zero. This means that b must not be zero, whereas a can have any
value except zero. In pseudo code, we would have the following script:

if (b.value == "" || b.value == "" && a.value == "") {
//suppress this calculation and all others depending on c
} else {
// do the calculations
}
But i do not understand how to fix this.

What dont you understand exactly, you seem to know how the if statement works already, so what exactly is the problem?

I am not sure why you are using the test you are in the if statement, I would have thought that if either 'a' or 'b' was 0 you would want it to fail, unless you want to end up with something like 0/99, where a = 0 and b = 99.

What is the difference between:

"This means that b must not be zero, whereas a can have any
value except zero"

What this says to me is that neither value should be 0.