i create a custom function

public double ConvertStringToDouble(String aString)

   out = Double.parseDouble(aString);
return out ;

but the out is not showing the Double from the String.

I modified the codes from here thinking i only need Double.parseDouble.
I copy and paste everything into custom function but it does not work ;D
I farmed the internet already, it is close but not working yet. any idea how to ConvertStringToDouble ?