Sum values by category when available in dataset with different months

[av9]

Hi, I have a scenario where I am trying to calculate the total amount per customer. My data is received in the following format. Each month I get a Total Amount per category per customer, and the Total is static, i.e I dont need to have a running total, I just take the value for each month.

Date	Customer	Category	Total Amount
30/08/2020	A	Web	$100
30/08/2020	A	Mobile	$0
30/08/2020	B	Web	$100
30/08/2020	B	Mobile	$100
30/09/2020	A	Web	$500
30/09/2020	A	Mobile	$500

So when I look at the data today I want the Totals for each customer to be: 

Combined Total @ Today
Customer A	$1000
Customer B	$200	As I haven't got the Sep 2020 data for customer B the total stays as per Aug 2020.

Next day: I refresh data and it looks like this: 

Date	Customer	Category	Total Amount
30/08/2020	A	Web	$100
30/08/2020	A	Mobile	$0
30/08/2020	B	Web	$100
30/08/2020	B	Mobile	$100
30/09/2020	A	Web	$500
30/09/2020	A	Mobile	$500
30/09/2020	B	Web	$200

So Total per Customer will be: 

Combined Total @ Today
A	$1,000
B	$300	this is made up of $200(Web-Sep2020) + $100(Mobile-Aug2020)

And so on it goes. once the Mobile data for September comes through I then replace the August mobile data

[DataInsights · Accepted solution]

@av9,

Try this measure:

Amount = 
VAR vMobileRows =
    FILTER ( Test1, Test1[Category] = "Mobile" )
VAR vMobileMaxDate =
    MAXX ( vMobileRows, Test1[Date] )
VAR vMobileLatestRow =
    FILTER ( vMobileRows, Test1[Date] = vMobileMaxDate )
VAR vMobileAmount =
    SUMX ( vMobileLatestRow, Test1[Total Amount] )
VAR vWebRows =
    FILTER ( Test1, Test1[Category] = "Web" )
VAR vWebMaxDate =
    MAXX ( vWebRows, Test1[Date] )
VAR vWebLatestRow =
    FILTER ( vWebRows, Test1[Date] = vWebMaxDate )
VAR vWebAmount =
    SUMX ( vWebLatestRow, Test1[Total Amount] )
VAR vResult = vMobileAmount + vWebAmount
RETURN
    vResult

Today:

The next day: