Cumulative balance per customer

Hello,

I have a table inclunding more then 10K rows and includinf the following columns:

- customer (more then 200 customers)

- invoice amount

- invoice date

- expected pay date of the invoice

I want to calculate the cumulative balance of every customer over time, based on the invoice date en expected payment date of the invoice, so I can measure the exposure over time per customer.

therefore, I created a Calender table for 3 years to measure the Exposure per customer. I was able to include 3 columns in this Calender table:

- total invoice amount per date 

- total expected payment per date

- total Outstanding (which is the total invoice amount - expected payment per date)

Now I want to make a measure which calculatea the cumulative amount and make it possible to filter per customer. 

However, it's not possible for me to create a measure to calculate the cumulative measure per customer.

Anyone who can help me? Is it because I've two different tables (1 with invoices per customer and 1 Calender table)?

thank you in advance