In a grid change the Selected Item Model properties but it should not reflect back in the grid unless user saves it

In a grid change the Selected Item Model properties but it should not
reflect back in the grid unless user saves it

I am working on a wpf application, where most of the screens consist of a
details grid and a form where the selected item of the grid is displayed.
In this details form the user can update the individual properties of the
selected item.
This is a MVVM application and in my view model i have exposed two
properties one is observable collection of the model which acts as item
source for the grid. and there is a Selected Item Model which binds to the
selected item of the grid.
Now my problem is when user changes any property of the selected item in
the details forms, it automatically reflects back to the grid, i have
tried changing modes of binding but nothing works.
I just want to make sure the selected item changes but it should not be
reflected back to grid unless user saves these changes.