<Grid Height="181" Name="grid1" Width="332" Column="1">

        <Button Content="Button" Height="23" HorizontalAlignment="Center" Name="button1" VerticalAlignment="Center" Width="75" Margin="70,103,186,55" >

            <Button.Triggers>

                <EventTrigger RoutedEvent="Button.Click">

                    <EventTrigger.Actions>

                        <BeginStoryboard>

                            <Storyboard>

                                <DoubleAnimation Storyboard.TargetProperty="Width" To="150" Duration="0:0:2" />

                            </Storyboard>

                        </BeginStoryboard>

                    </EventTrigger.Actions>

                </EventTrigger>

            </Button.Triggers>

        </Button>

    </Grid>