Need assistance writing a calculation with two conditions

[Megan243494739njt]

This one is a little beyond me so I'm hoping someone can help -

I'm working with 5 fields, I'll label them "fieldA"-"fieldE" for simplicity sake. 

Here is what I'm after: fieldD = fieldB, unless: 1) fieldE is greater than 50,000 and 2) fieldB is null, then fieldD = fieldC. 

Field D is where the calculation would be. 

Example 1:

fieldA: $100,000

fieldB: null (not sure how to express this in the field itself, does null or N/A work, or leaving it blank wihtout it reading as 0?)

fieldC: $60

fieldD: (result should be $60)

fieldE: $150,000

Example 2:

fieldA: $95,000

fieldB: $20

fieldC: (this will default as a 0.00)

fieldD: (result should be $20)

fieldE: $90,000

Thanks all of you wonderful people! 

[try67 · Accepted solution]

Null, an empty string and zero are not the same things, so it's important to know what you're dealing with.

Assuming it's a blank field, you can use this code as the custom calculation script of fieldD:

var fieldB = this.getField("fieldB").valueAsString;
var fieldC = this.getField("fieldC").valueAsString;
var fieldE = this.getField("fieldE").valueAsString;

if (Number(fieldE)>50000 && fieldB=="") event.value = fieldC;
else event.value = fieldB;

[try67]

PS. fieldA doesn't seem to have a role in this formula...