Disable RadcomboItems MVVM

[Ubuntu]

Dear All,
    I have a RadComboBox as follows:
    

<telerik:RadComboBox x:Name="cbxTaxType" IsEditable="True" IsReadOnly="True" Margin="0,0,0,5" Grid.Row="5" Grid.Column="1" Grid.ColumnSpan="3"
    ItemsSource="{Binding TaxType,Mode=TwoWay,NotifyOnValidationError=True,ValidatesOnExceptions=True}"
    SelectedValue="{Binding Path=CurrentTaxpayer.TaxType, Mode=TwoWay,NotifyOnValidationError=True,ValidatesOnExceptions=True}"
    SelectedValuePath="ID"
    IsEnabled="{Binding Path=IsLocal, Converter={StaticResource intToBooleanConverter}, ConverterParameter=false}"
    DisplayMemberPath="TaxTypeAr"/>

    I need to disable a specific value represented by RadComboBoxItem depends on specific condition.
    How is this possible using MVVM.

Appreciate any help.