vertical layout height does not fill entire TD

Hi I have a table where in the third column i have to dispaly a list of objects. Now in the second column i have a vertical layout . When the user clcks on the second column i have to change the background colur of the column and display a menu (popup). Now the vertical layout is not spanning the entire TD. below is the code for column generator

public Component generateCell(final Table table, final Object itemId,
final Object columnId) {

final List<TreatmentObjective> objectives = (List<TreatmentObjective>) table
.getItem(itemId).getItemProperty("treatmentObjectives")
.getValue();

final VerticalLayout verticalLayout = new VerticalLayout();
verticalLayout.setWidth("100.0%");

for (final TreatmentObjective to : objectives) {
Panel panel = generatePanel(to, table);
verticalLayout.addComponent(panel);
}

return verticalLayout;
}

How can i acheive this. I cannot make a single column to get selected, this is how i want to bypass/ make user believe that column is selected.
Find attachment to get a clear picture of the problem