Creating a dynamic measure to count backwards

Hello! 

I have some data with orders that is yet to be completed, and orders that have already been completed.

Here I have made a figure showing the total amount of orders that is yet to be completed, however I would like to make a bar chart that shows how many orders is yet to be completed week for week, within the last 10 weeks.

I want this in order to get insight on whether the stack is getting smaller or larger (If we complete the orders faster than they come in). 

I figured I would make a measure that counts the amount of orders completed per week, aswell as a measure that counts how many orders is received per week, and lastly one that calculates the difference between the two. 

Now as you can see here, I have the 494 orders for the current week, I would like to make some measure that tracks backwards, so it says currently we have 494 orders, last week we had 498 orders (As we completed 4 more orders than we received during the week) and then for the week before that, it should take the 498 orders and calculate the difference so it would be 528 orders (As we completed 30 more orders than we received)

Heres a snip of how the measurements work currently:

I apologize if I didn't give sufficient information for this, however I am rather new at PowerBI.

Any suggestions?