Can I prevent "NaN" from appearing in numerical entry?

Hi there

I would like to add up a couple of numbers in Storyline 3.  I thought I could use the number entry field to do this? The number goes in fine but when I try to add the value that was entered to a variable to add up a score, I get the NaN issue.

Is there a simple way around this yet?  I am really suprised Storyline can't add a number(s) to a variable.  Maybe I am missing something here?

I have tried the following workarounds:

1. setting the value of the total variable to 0 when the timeline starts.
2. changing the state of a tick/check image if the correct number is entered to normal.
3. using a drop down question but I have several of the same numbers including 0 to select.

None of these work.  I don't quite get how to apply the javascript so haven't tried that.  Any explanation on how to add that would be helpful.  e.g. do you just add the script and replace  inH1 =  numericentry1 variable?

Many thanks for any help with this.

Amanda