using custom new, edit, delete, commit, cancel buttons for dataform

[Dhiraj]

Hello,
I am currently working on silverlight business application using MVVM architecture and EDM using Domainservice .
I want to implement functionality somewhat like,

1. The Gridview should display the data in table.
2. On selecting the row, details should be displayed in rowdetailstemplate with readonly mode.
3. On Edit button click the DataForm should change its mode to editable.
4. On Save or Cancel it should allow to commit or rollback resp. the data for current context and turn to readonly again.
5. On delete button click, it should delete the current record

I have finished upto the 2 step and not getting how to switch between DafaForm modes using MVVM, by making use of buttons added below the DataForm in stackpanel.

Since I am at beginner stage any help would be appreciable.
Thanks