How to make the word appear / disappear automatically?

[leafchan]

Initially, there are three text field.

If I input any word or number in field A, for example

Finally, the word " - " will be automatically appeared in field B without any input.

Similarly, If data in Field A is deleted, the word "-" will be removed automatically.

How to make the relevant code in fillable PDF? Thank you very much!

[try67]

As the custom validation script of field A enter this code:

this.getField("B").value = (event.value=="") ? "" : "-";

[leafchan]

Thank you for your reply.

Do I need to add the code below?

if.....else

event.rc = false

event.value=""

Thank you very much

[try67]

No. Use the code I provided.