how to copy documents from one document library to another document library whern field value changes within the site in sharepoint 2010?

Create Document library:

How do I create a document library in SharePoint?

The following article explains how to create a document library in SharePoint. A document library is created to store a collection of documents or files that you want to share. Document libraries support features such as sub-folders, file versioning, and check-in/check-out.
Note: SharePoint will only work properly in Internet Explorer.

To create a document library, please follow these steps:

1. Open a web browser and log into SharePoint.
2. Click Site Actions and select Create.
3. Under Libraries, click Document Library.
4. Enter the necessary information:
   • Name: enter a name for the library
   • Description: enter a description of the purpose of the library
   • Navigation: click Yes if you want a link to this library to appear on the Quick Launch bar
   • Document Version History: click Yes if you want a backup copy of a file to be created each time a file is checked into the library
   • Document Template: specify the type of file used as a template for new files in this document library
   
5. Click Create.

7.Inside Document library add documentset and upload Few documents to the documentset.
8. create a column Document_Status as Choice field.(under development,ready for review, move to TARGET folder)
 Once change the status of the field copy the documents from one documentlibrary to another location within the same site.

9.Create ListWorkflow in sharepoint designer
10.wrokflow steps:
1.if current item field equals value(condition)
2.send document set to repository(ACTION)
3.set field in current item.(ACTION)
save and publish the workflow.

11. Attach the workflow to the documentset and change the status.