Analysis :: Calculation Based On Dimension Value

Need to resolve this calculation, which I would believe is something very common on SSAS environments. 

Like many companies, my company has different ways of calculating Sales and the two I want to focus are Sales Gross and Sales Net. 

At a high level, we calculate Sales Gross as Sales with returns, and Sales Net as Sales without returns.

We have an attribute called Order Type that has various types of orders a user can execute with my company. One of them is Returns. If you return something back to us, we record that as a return line on the sales table. With that, we can calculate that return, breaking data down by Order Type, such as:

Order Type Line Total

Mail Orders $ 776,655.44

Internet Orders $ 2,211,334.00

Call Center Orders $ 11,223,344.00

Credit Orders  $ (55,666.00)

Today, to calculate Sales Gross and Sales Net, we are creating two dimensions: DimSalesGross and DimSalesNet. 

To calculate Sales Gross, we leave the data at the natural state, not making any changes to mappings. 

To calculate Sales Net, we map Credit Orders to Call Center Orders at the ETL level, getting a Net value for sales (Orders - Returns), however, I doubt this is the correct way of doing. 

I would like to have a Line Total Net / Line Total Gross calculation, which would be based on the Order Type value.

Perhaps using a CASE statement in MDX? Is the above possible?