Combo box binding using silverlight

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Silverlight

combobox

Binding

Hello guys, so I have two comboboxes:

<ComboBox Height="35" HorizontalAlignment="Left" Margin="343,67,0,0" Name="comboBox2" VerticalAlignment="Top" Width="273" SelectionChanged="comboBox2_SelectionChanged"    >
            <ComboBox.Items>

                <ComboBoxItem IsSelected="True" Content="Trial"  />
                <ComboBoxItem IsSelected="True" Content="Limited" />
                <ComboBoxItem IsSelected="True" Content="Pernament" />




                </ComboBox.Items>
        </ComboBox>

and

<ComboBox Height="35" HorizontalAlignment="Left" Margin="343,125,0,0" Name="comboBox1" VerticalAlignment="Top" Width="273" SelectionChanged="comboBox1_SelectionChanged">
            <ComboBoxItem Content="3 Months" IsSelected="True" />
            <ComboBoxItem Content="6 Months" />
            <ComboBoxItem Content="12 Months" />
            <ComboBoxItem IsSelected="True" Content="-" />
        </ComboBox>

I am trying to bind them for example if value of first box isn't Limited, second combo box should be disabled, and if Limited is selected in text box this date + months chosen must be displayed. Thanks for help in advance