Import .CSV data source with 2 matrix

I think the only way you will be able to do this is to add a Business Rule to all of the UD6 columns on the Data Source. You add a value to Globals to identify the column number and then use a BR in the transformation rule for the account to look up the column number. The GolfStream application has examples of saving and retrieving values from Globals  (XFR_Delimited_Get_Amount and XFR_Delimited_Put_Entity).

In brief the code for the first UD6 column will be something like this:

globals.SetStringValue("UD6Instance", "0205")

and the others will be:

globals.SetStringValue("UD6Instance", "0210")

Then in the BR for the Account Transformation Rule you do something like this:

Return globals.GetStringValue("UD6Instance") 

Check the Transformation Sequence order on the cube (Cubes | cube | Integration tab). The UD6 dimension must be processed before the Account dimension.