Error Message - Value Entered Does Not Match Format of Field

Question

I keep getting an error message in Adobe Pro X: "The value entered does not match the format of the field [JF13]".
I have JF13 programmed as follows:
On Calculate tab:
if(Number(this.getField("ck4").value) > 0) this.getField("JF13").value = Number(this.getField("FL019").value); else this.getField("JF13").value = " ";
It is programmed this way so if the user checks the check box before the field, only then will JF13 populate a value, which pulls from FL019. I also have the settings set to "number" because the data needs to display as a dollar amount $xxx.xx.
FL019 is a hidden field on the form which pulls a dollar amount from a Mainframe, and its settings are also set to "Number" :
I get four pop up windows with the above mentioned error message, and the only way to make the message stop is to remove the "number" format from the fields. However, when this is done, if any number which ends in a zero is entered, it cuts off the zero. This is not acceptable either.
Is there some sort of script I could add or some other way to prevent both the error message and the cutting off of the zero on JF13?
I am not very proficient with javascript, so any assistance would be appreciated!

Answer 1

Thank you so much for your response!!
Forgive me for my lack of knowledge - but where exactly would I add that in the script?
I tried it like this:
if(Number(this.getField("ck4").value) > 0) this.getField("JF13").value = Number(this.getField("FL019").value); else this.getField("JF13").value = ""(empty string);
And I got an error saying I was missing a parenthesis. Should it go somewhere else or am I completely off?