Disable Combo box of user control in wpf

Hi,

I have one user control which contains Two comboobx, six textbox and 4 labels.I
I have added this user control in main window xaml like this:

    <Grid Height="Auto" HorizontalAlignment="Left" Margin="0,156,0,0" Name="grid1" VerticalAlignment="Top" Width="320"  />
        <Grid Height="Auto" Grid.Column="1" HorizontalAlignment="Left" Margin="0,156,0,0" Name="grid2" VerticalAlignment="Top" Width="320"  />
        <Grid Height="Auto" Grid.Column="2" HorizontalAlignment="Left" Margin="0,156,0,0" Name="grid3" VerticalAlignment="Top" Width="320" />
        <Grid Height="Auto" Grid.Column="3" HorizontalAlignment="Left" Margin="0,156,0,0" Name="grid4" VerticalAlignment="Top" Width="320" />

I have Created view model for UserControl which name is UserControlViewModel and main window has view model which name is MainViewModel.

I have created object of usercontrol in mainViewModel.

My question on run time I have to disable combo box1 from UserControl in grid2 and grid4.

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vikas sharma AB