Problems auto-filling a text box

Question

Hi,
I am trying to populate a text field with either "Yes" or "No" based on the value placed in another text field. If the value in [textfield 1] is greater than 0, I want a "No" to appear in [text field 2] and if the value of [textfield 1] = 0, I want a "Yes" to appear in [text field 2]. If [textfield 1] is blank, I want [textfield 2] to be blank. I have put the following code into the Custom Calculation area of [textfield 2]:
var a = this.getField("textfield 1").value;
if(a=="") event.value = "";
else if(a>0) event.value = "No";
else if(a==0) event.value = "Yes";
Currently if the value from [textfield 1] is greater than 0 a "No" will appear, but the field remains blank if the value of [text field 1] = 0. I'm not sure why this is. This code has worked for me before when the value conditions are different. Is it something to do with the 0?
I also want some other fields to be visible when [textfield 2] is populated with a "No" in the box and hidden when [text field 2] is populated with a "Yes". This is the code I used in the custom  validation script:
if (event.value =="Yes") {
     this.getField("textfield 3").display = display.hidden;
     this.getField("checkbox1").display = display.hidden;
} else if(event.value =="No") {
     this.getField("textfield 3").display = display.hidden;
     this.getField("checkbox1").display = display.hidden;
Again this code has worked for me for other fields. I'm thinking it doesn't work now because I don't have the Calculation Script working yet?
Any help would be greatly appreciated. Thanks!

Answer 1

It seems as though in my calculation code this line:
if (a=="") event.value = ""
conflicts with this line:
else if(a==0) event.value = "Yes".
I changed the values in my code so that if a>10 it would return a "No" and if a<10 it would return a "Yes" and it worked perfectly. However, when I use the above code (a==0, it just leaves the box blank. I would take out the first line of code (a==""), but I would like the box to be blank until data has been entered into the form.