How to get correct Incoming Balance / Balance Sheet

Thank you for your answer lbendlin. 

I have tried the approach you listed, but I have not quite managed to find the correct solution. 

1. My table looks like this: 

As you can see I now have, as you suggested, a column in the format YYYYMM, this is the one I have linked to my datetable. There is also a column for account in every row in the table above.  IB is incoming balance and CB is closing balance. 

2. I have tried to make the measure you outlined above, but I have not managed to make it work properly.

3.  I have created this measure to calculate the maximum YYYYMM for the account that is smaller than my selected filter: 

MAXYearMonth =

var YearMonth = MAXX(ALLSELECTED('Datotabell - Master'), 'Datotabell - Master'[Date])

var Account = SELECTEDVALUE(Ac[AcNo])

Return

CALCULATE(MAX(AcBal[dateFormat]), FILTER(ALL('Datotabell - Master'),'Datotabell - Master'[Date] < YearMonth))

 

This gives me the last date there was a transaction on the specific account: 

 

 

As you can see there has not been any transactions on account "1937" since 2019-12, but the CB registered in my transaction table for this account is what I want to be shown as IB if I i.e. choose 2021 as year.

4. After this I tried making a measure that gives me the last calculated closing balance for the account where YYYYMM is smaller than selected date.