Only include figure if filter selected

[tadisweb]

Hi

Firstly, worth mentioning I'm fairly new to Qlik Sense and not that advanced a user.

I have managed to put together a running balance formula:

rangesum( above(

  Sum({$<[Transaction Type]={'credit'},[GL]-={'Agency'} >}([Amount]))-

    Sum({$<[Transaction Type]={'debit' },[GL]-={'Agency'} >}(-[Amount])

    ),0,rowno()))

and I have a row in my data for opening balance eg 10000 with a date value of 01/01/2017.However if I filter to show only 2018, the running balance stops working as it no longer includes the 10000 I had set above.

Is there a way to set an opening balance for 01/01/2018 that is only shown if I filter to 2018 but which disappears if other years are selected?

Thanks