Insert calculated despatched quantity column in transaction table

[Debo1996]

Hi, 

I have a transaction table which stores two types of transactions sales and sales order. (assuming dealing in goods)

Sales Order is a transaction which give details of the order placed by customer

Sales is a transaction which takes a sales order as reference and gives details of the actual items shipped to the customer (item quantity in sales can only be less than or equal to quantity in sales order)

I want to add a column which gives the despatched quantity in front of the order items (using reference given in the sales) which can make it easier to calculate pending order quantity.

Voucher Type Id:

S - Sales

SO - Sales Order

Transaction Table 

I need help with the Dax formula for the column "Despatched Quantity?"

Thanks

[lbendlin]

Please provide sanitized sample data that fully covers your issue.
https://community.powerbi.com/t5/Community-Blog/How-to-provide-sample-data-in-the-Power-BI-Forum/ba-...
Please show the expected outcome based on the sample data you provided.

https://community.powerbi.com/t5/Desktop/How-to-Get-Your-Question-Answered-Quickly/m-p/1447523