Synchronising cursors

Hi there. I have many chartwindows each with price and volume panes. Each chart has own ViewModel instance as datacontext. I need cursor to be synchronized in each chart between price chart and volume chart.
If I write in xaml <s:ModifierGroup s:MouseManager.MouseEventGroup="xxx"> it synchronizes all cursors of all charts. So I’m trying to do the following:

<s:ModifierGroup s:MouseManager.MouseEventGroup="{Binding MyMouseGroup}">

In ViewModel (part of code from different blocks):

private string _myMouseGroup;
_myMouseGroup = Guid.NewGuid().ToString();
       public string MyMouseGroup
        { get { return _myMouseGroup; }  }

But it’s not worked, Cursors are not synchronized in one chart. I understand that MyMouseGroup should be not string type but dependency property though in Xaml I can use any string. But I don’t have enough programming knowledge to figure out how to do it. Please help with that MyMouseGroup property.