Accessing the instance of a custom control within a static method

In WPF I have created a custom control for a button.
I would like this button to become ‘enabled’ when a target datagrid has some cells selected, otherwise it should become ‘disabled’.

This is my code:

public class MyCustomButton: Button
{

    public DataGrid TargetDataGrid
    {
        get { return (DataGrid)GetValue(TargetDataGridProperty); }
        set { SetValue(TargetDataGridProperty, value); }
    }
    public static readonly DependencyProperty TargetDataGridProperty =
        DependencyProperty.Register("TargetDataGrid", typeof(DataGrid), typeof(MyCustomButton), new PropertyMetadata(new PropertyChangedCallback(OnTargetDatagridChanged))); 

    private static void OnTargetDatagridChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        if (e.OldValue is DataGrid oldGrid)
        {
            oldGrid.SelectedCellsChanged -= DataGrid_SelectedCellsChanged;
        }
        if (e.NewValue is DataGrid currDg)
        {
            currDg.SelectedCellsChanged += DataGrid_SelectedCellsChanged;
        }
    }

    private static void DataGrid_SelectedCellsChanged(object sender, SelectedCellsChangedEventArgs e)
    {
        if (sender is DataGrid dg && dg.SelectedCells.Any())
        {
           // how can I disable/enable this button since we are in a static method? 
           // IsEnabled = true
        } 
        else 
        {
           // IsEnabled = false
        }
    }
}

>Solution :

Do not declare the event handler as a static method:

private static void OnTargetDatagridChanged(
    DependencyObject d, DependencyPropertyChangedEventArgs e)
{
    var button = (MyCustomButton)d;

    if (e.OldValue is DataGrid oldDg)
    {
        oldDg.SelectedCellsChanged -= button.DataGrid_SelectedCellsChanged;
    }
    if (e.NewValue is DataGrid newDg)
    {
        newDg.SelectedCellsChanged += button.DataGrid_SelectedCellsChanged;
    }
}

private void DataGrid_SelectedCellsChanged(
    object sender, SelectedCellsChangedEventArgs e)
{
    IsEnabled = sender is DataGrid dg && dg.SelectedCells.Any();
}