public Binding IsCheckBoxEnabledBinding { get; set; }

Public Property IsCheckBoxEnabledBinding As Binding

<dxg:TreeViewControl ShowCheckboxes="True"
                     AllowRecursiveNodeChecking="True"
                     CheckBoxFieldName="OnVacation"
                     IsCheckBoxEnabledBinding="{Binding Enabled}"
                     .../>

public class Employee {
    public int ID { get; set; }
    public string Name { get; set; }
    public bool OnVacation { get; set; }
}
public class EmployeeDepartment {
    public string Name { get; set; }
    public ObservableCollection<Employee> Employees { get; }
    public bool Enabled { get; set; }
}

Public Class Employee
    Public Property ID As Integer
    Public Property Name As String
    Public Property OnVacation As Boolean
End Class
Public Class EmployeeDepartment
    Public Property Name As String
    Public ReadOnly Property Employees As ObservableCollection(Of Employee)
    Public Property Enabled As Boolean
End Class