Mass upload of Materials (articles) using MR21 via BAPI/ LSMW

Hi Gurus,

I was hoping you could help me in setting up an LSMW to Mass change articles (MR21 in mass) for 10000's of materials in a Retail environment

I have now :

1. Setup the Object Attributes
   1. I went with the IDOC method using Message Type MATERIALVALUATION_PRICECHANGE and Basic Type MATERIALVALUATION_PRICECHANGE01 with periodic data transfer since we will be doing it for store by store after Stock Takes of Stores are completed
2. Maintain Source Structure
3. Maintain Structure Relations
   1. E1MATERIALVALUATION_PRICECH
      1. E1BP_MATVAL_PRICEDATE (Price Change Date)
      2. E1BPMGVMATNR_COPY (BAPI Structure)
      3. E1BP_MATVAL_PRICES
4. Now I need to use a sample file and thsi is where I am stuck and need help to a simple file structure that I can convert for upload to allow me the SITE/ARTICLE/VALUATION CLASS/VALUE I woudl assume?

Any help in the format of the file and further steps I may have omitted would be greatly appreciated.