Subsets with measures

I want to calcualte only sum Shipment Quantity when there was a return.

So Overall Shipment Quantity is 760 (50+100+340+270)
Overall Return is 65 (35+5+25)

So return % is: 65/760 = 8.55% which is easy to calculate.

Now, the problem is: If I only want to calculate % of shipment, if there is a return, then it will be:

420/760 = 55% (exclude the customer which didn't have any returns).

where 420 = 50 +100 +270  (A, B and D)
overall shipment 760 = 50 + 100 + 340 + 270

How do I calculate this?

Here are my formulas:

Shipment Quantity =
VAR TotalSales =
    CALCULATE (
        SUM ( 'Sales Order Detail'[Custom Quantity] ),
        'Order Type'[Order Type Transaction Group] = "Sales"
    )
RETURN
    TotalSales

Return Quantity =
VAR TotalReturns =
    CALCULATE (
        SUM ( 'Sales Order Detail'[Custom Quantity] ),
        'Order Type'[Order Type Transaction Group] = "Return/Dump"
    )
RETURN
    TotalReturns

Return % =
VAR TotalReturnDump =
    CALCULATE (
        SUM ( 'Sales Order Detail'[Custom Quantity] ),
        'Order Type'[Order Type Transaction Group] = "Return/Dump"
    )
VAR TotalSales =
    CALCULATE (
        SUM ( 'Sales Order Detail'[Custom Quantity] ),
        'Order Type'[Order Type Transaction Group] = "Sales"
    )
RETURN
    ABS ( DIVIDE ( TotalReturnDump, TotalSales, BLANK () ) )

I created this measure as well:

Brand Product Line Return Flag =
IF ( ISBLANK ( [Return Quantity] ), "NO", "YES" )

But I can't use this in Filter function as this is a measure.

Any help?

Like in the picture  below,

First table gives me all the Shipments and their Return values.

2nd table gives me only Shipments where Returns happen.

Both the tables have same Return quantity. Only Shipment numbers are changing due to our logic.

And  I want to calculate 3,54,539 /1,078230 and so on and so forth....

Thanks,
Ritesh