Using selection date as cut-off point for open balances

Hello,

I would like for my Pivot table to use a user selection as a cut-off point for the data presented. 

For instance, if I have a client who owes money from September, upon selection of October, I would like to view the balance due from both September AND October. However, anything beyond October would be ignored. 

I believe my issue lies in the relationship between my Fact and Date Dimension (Many-to-one respectively). The way I perceive this working is the relationship is only taken into account prior to the selected value, otherwise ignore it. The reality of the situation is that the selection is being considered so no prior months are included. 

I've tried the ALL, ALLEXCEPT, and CROSSFILTER Functions to no avail. 

Here is my code:

CALCULATE(sum('Deliver TRANSACTION_FACT_UNION'[Amount]),
'Deliver TRANSACTION_FACT_UNION'[TxnType] = "Invoice",
FILTER('Deliver TRANSACTION_FACT_UNION','Deliver TRANSACTION_FACT_UNION'[TxnDate] <= [Open Invoice Date Slicer]),
'Deliver INVOICE'[IsPaid] = false(),
'Deliver INVOICE'[IsPending] = false(),
'Deliver TRANSACTION_FACT_UNION'[TransactionSummaryFlag] = TRUE())

Any suggestions?

Thanks!