Share the same object between two windows with out refresh all instance of the same object in the forms, MVVM pattern

I have a problem with the pattern MVVM in C# windows forms, I have a form called A that have an object binding, at this point all is ok, that form in another windows is opened like showdialog but when this happen the values ​​of form A are updated to the same values ​​of the form that was opened as showdialog, there is a way to show the info in the showdialog with out updated the values of the form A? I know that this is normal behavior of the MVVM design pattern, but is it possible to cancel the update of form A?